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Home »» Science Powerhouse »» Audio Glossary
Mindfiesta Power House Hi  Study  Buddies,
Welcome to your page – your study space. If you are about to enter into the gravity of subjects then this space is your warm-up zone. If you have made a stop here on your way back from the content section, this will be your 'Science / Math lounge for learning'.
A B C D E F G H I J K L M N O P Q R S T U V W X Z
A
Abiotic : Nonliving.
Abrasion : A type of weathering in which windblown particles wear down rock.
Absolute humidity : The actual amount of water vapour in the air.
Absolute magnitude : The intrinsic brightness of a star, its brightness as it would appear at a standard distance away from Earth.
Absolute zero : A theoretical temperature that scientists believe is the lowest attainable, equaling -273.15°C.
Abyss : The deep ocean bottom.
Abyssal zone : Region of the ocean 2,000 to 6,000 meters deep in which rays and sea cucumbers live.
Acceleration : A change in velocity, either an increase (positive acceleration) or a decrease (negative acceleration).
Acid : A compound that produces hydrogen ions when dissolved in water, or more generally, a compound that can donate a proton when it combines with another substance. Acids turn litmus paper red and have a sour taste.
Adenosine triphosphate : A compound of adenosine and three phosphate groups that stores energy in cells. Also called ATP.
Adhesion : The property of a liquid that results from the attraction of its atoms or molecules to the atoms or molecules of another substance.
Aestivate : To stay inactive during the heat of summer.
Agar : A gelatin like substance used in laboratories to grow bacteria.
AIDS : (Acquired Immune Deficiency Syndrome), a disease that results from severe damage to the body′s immune system, be believed to be caused by the human immune − deficiency viruses HIV−1 and HIV−2.
Air mass : A large body of air with a nearly uniform temperature and humidity that forms over an area of land with a fairly constant temperature.
Algae : Simple organisms, some of which are unicellular and float free in water, some of which are multicellular. Blue−green algae are classified as Monera: all other algae are classified as Protista. Plural of alga.
Alimentary canal : The long tube that forms the main part of the human digestive system, beginning at the mouth and ending at the anus.
Alkali metal : One of the metallic elements in group 1A of the periodic table.
Alkaline-earth metal : One of the metallic elements in group 2A of the periodic table.
Allele : One of two forms of a gene that helps decides an inherited characteristic.
Alloy : A combination of metals.
Alternating current : An electric current in which the electricity flows regularly in one direction and then the other. Also called AC.
Alternation of generations : The cycle of sexual reproduction in plants that involves two distinct generations or phases.
Alveoli : Thin walled air sacs in the lungs where the exchange of carbon dioxide and oxygen occurs. Plural of alveolus.
Amino acid : A small molecule containing carbon, hydrogen, nitrogen and oxygen that makes up proteins.
Amoeba : A simple protozoan that uses pseudopods to move and capture food.
Ampere : A unit of measure of an electric current.
Amphibian : An animal that lives part of its life in water and part on land.
Amplitude : The distance a vibrating object travels from its position of rest, or equilibrium point.
Anabolism : The process by which cells make complex organic molecules from smaller units; constructive metabolism.
Anaerobic : Living or occurring without oxygen.
Analytical chemistry : The study of the properties of chemical substances and the structure and composition of compounds and mixtures.
Angiosperm : Flowering plants.
Antibiotic : A drug that weakens or destroys bacteria and other organisms, often used to treat disease.
Antibody : A special protein released into the blood to fight foreign bacteria or viruses
Antigen : A foreign substance that elicits the release of antibodies.
Aorta : The largest artery in the body, through which blood leaves the left side of the heart.
Apex : The tip of a plant.
Apical meristem : The actively dividing cells that form the growth area at the tip of a plant.
Apparent magnitude : The brightness of a star as seen from Earth.
Apparent motion : The difference in motion between an observer and the observed object.
Archaebacteria : Microscopic organisms that can live in warm, oxygen free environments.
Arteriole : A small blood vessel that leads into capillaries.
Artery : Any of the blood vessels that carry blood from the heart.
Artificial satellite : An object made on Earth that orbits Earth or some other body in space.
Asexual reproduction : Reproduction involving one parent that leads to a genetically identical offspring.
Asteroid : A relatively small planetary body that revolves around the sun.
Asteroid belt : A zone lying between the orbits of Mars and Jupiter, in which most asteroids lie.
Astronomical unit : A unit of measure equaling the average distance from the sun to Earth, about 150 million kilometers. Abbreviated A U.
Atmosphere : The mass of gases that surrounds Earth. Also called air.
Atmospheric pressure : The force of gases in the air pressing down on Earth.
Atom : The basic unit of matter.
Atomic mass : The mass or quantity of matter, of an atom expressed in atomic mass units (amu).
Atomic number : The number of protons in an atom.
ATP : A compound of adenosine and three phosphate groups that stores energy in cells.
Atrium : An upper chamber of the heart. Also called auricle.
Aurora australis : The southern lights, a display of lights in the sky of the Southern Hemisphere produced when charged particles in the solar wind react with Earth′s magnetosphere.
Aurora borealis : The northern lights, a display of lights in the sky of the Northern Hemisphere produced when charged particles in the solar wind react with Earth′s magnetosphere.
Auxin : A hormone that affects the growth of plants.
Bacilli : Rod shaped bacteria. Plural of bacillus.
Bacterial spore : An inactive bacterium formed during unfavorable conditions that may become active again when conditions improve.
Base : A compound that produces hydroxide ions when dissolved in water, or more generally, a compound that can accept a proton when it combines with another substance. Bases turn litmus paper blue, have a bitter taste, and feel slippery in water.
Bathyal zone : Region of the ocean extending from the edge of the continental shelf to 2,000 meters deep, in which few plants but some animals can live.
Benthos : Organisms that live on the ocean floor.
Big bang : The violent and enormous explosion that most astronomers believe marked the beginning of the universe.
Big crunch : The condensation of all matter into one incredibly dense, hot mass that some astronomers believe will mark the end of the universe.
Bilateral symmetry : Having similar left and right sides.
Bile : A liquid made in the liver and stored in the gall bladder that aids digestion by emulsifying fats.
Binary star : A star that appears in a pair. Also called double star.
Biochemistry : The study of the chemical processes that take place in living things.
Biome : A natural community of animal and plant life, determined by weather, soil and other factors.
Black dwarf : A dead star made of matter condensed into a small, dense mass with no energy left to emit.
Black hole : A remnant of a star so condensed that its gravity is strong enough to prevent light from escaping it.
Blade : The Hat pan of a leaf.
Bone marrow : The soft, fatty core of bones.
Boreal forest : A biome characterized by swampy, coniferous, evergreen forest land with long, cold winters.
Boson : A subatomic particle that transmits a force between particles.
Breccia : A type of sedimentary rock made up of jagged fragments.
Bronchi : Be two large main tubes that branch out from the trachea, each entering a lung. Plural of bronchus.
Bronchiole : An extremely thin tube branching out from the bronchi in the lungs.
Budding : A form of asexual reproduction in which a small projection extending from an organism develops and then detaches from the parent organism as a separate individual
Buoyant force : A force that lifts an object in a fluid, equaling the weight of the fluid displaced by the object.
Calyx : The structure that surrounds the unopened bud of a dower.
Cambium : The layer of cells growing between the bark and wood of a tree or shrub.
Canopy : The overhead covering of a rainforest formed by the tops of trees.
Capillarity : The tendency of a liquid to move into and out of tiny, hollow passageways.
Capillary : One of many tiny blood vessels that connect arteries and veins.
Carbohydrate : A macromolecule consisting of carbon, hydrogen, and oxygen that serves as the principal energy source for most living things. Sugars and starches are carbohydrates.
Cardiac : Having to do with the heart.
Carnivorous : Describing a meat eating organism.
Cartilage : The tough, elastic substance forming part of the skeleton of vertebrates. Also called gristle.
Cartilaginous : Having a skeleton of cartilage, as a shark.
Catabolism : The process by which cells break down large molecules into smaller units, thereby releasing energy that the cell may use to build other large units: destructive metabolism.
Catalysis : The process in which a substance increases the speed of a reaction.
Catalyst : A substance that increases the speed of a chemical reaction but remains unchanged by it.
Cell : The basic unit of life.
Cell membrane : The extremely thin covering of a cell. Also called plasma membrane.
Cell wall : The covering that surrounds the cell membrane in plant cells.
Cellular respiration : The process in which the products of digestion arc broken down into simpler materials and energy by cells.
Cellulose : A substance that makes up the cell walls of most plains.
Cenozoic Era : A period in Earth′s history, the most recent geological era that began about 63 million years ago and continues today.
Centrifugal force : The pull on a circling object to move in a line away from the centre around which ii is moving.
Centriole : A structure near the nucleus of a cell that forms one end of the fibre spindle during cell reproduction.
Centripetal force : The pull on a circling object toward the centre around which it is moving.
Centromere : A ring like structure that holds together the two chromatids during cell reproduction.
Chaparral : A biome characterized by shrubs and small trees with hot, dry summers and cool, wet winters.
Chemical bond : An attractive force that holds the atoms of a molecule together.
Chemical evolution : A theory that life on Earth developed through a series of chemical reactions in the atmosphere and oceans.
Chemical reaction : A process in which the molecular or ionic structure of one substance is changed, forming a different substance.
Chinook : A warm, dry wind that flows down the eastern slopes of the Rocky Mountains in the United States.
Chlorofluorocarbon : A gas composed of chlorine, fluorine and carbon that can deplete the protective ozone layer in the atmosphere. Also called CFC.
Chlorophyll : The green pigment in plants that absorbs energy from sunlight for use in photosynthesis.
Chloroplast : A structure in plant cells that contains chlorophyll.
Chromatid : One of the two identical strands of a chromosome that has replicated prior to cell reproduction.
Chromatin : Material in a cell that draws together to form chromosomes.
Chromosome : A string of DNA and proteins that carries genes.
Chromosphere : The middle layer of the sun′s atmosphere.
Cilia : Tiny, hair like projections.
Circuit : The path of an electric current from its source and back again.
Cirque : A circular shaped hollow carved out by a glacier.
Cirrus : A high, wispy cloud formed entirely of ice crystals.
Citric acid cycle : A series of reactions in a cell in which pyruvic acid produced by glycolysis is used to create carbon dioxide, water, and energy stored as ATP. Also called the tricarbaxylic acid cycle.
Clastic : Made from rock fragments ranging in size from coarse boulders to fine grains of sand.
Cleavage : The property of splitting into pieces with flat surfaces.
Clone : 1) Any group of organisms produced asexually from a single ancestor.
2) Exact genetic copy of another.
Cluster : A group of galaxies held together by gravity.
Cocci : Spherical−shaped bacteria. Plural of coccus.
Codon : A basic segment of the genetic code consisting of three bases representing one amino acid.
Coherence : Describing light that spreads little and has one colour.
Coinage metal : A metallic clement in group IB of the periodic table, so called because these metals are used to make coins.
Cold-blooded : Having blood that is always about the same temperature as the surrounding air or water.
Colloid : A suspension that contains extremely small particles. Homogenized milk, paint, and blood are colloids.
Coma : The hazy cloud around the nucleus of a comet.
Combustion : Burning, a chemical reaction in which heat causes the carbon and hydrogen in a substance to combine with oxygen in the air, producing heat, light, carbon dioxide, and water vapour.
Comet : A small, frozen chunk of gas, dust, and ice that revolves around the sun.
Community : All the life forms that inhabit a particular area.
Compound : A substance that is composed of at least two different elements, formed when atoms of the elements bond.
Compression : An area where waves are squeezed together.
Condensation : The act of a cooling gas becoming a liquid.
Conduction : The process by which some form of energy moves from one area to another.
Conglomerate : Sedimentary rock formed from worn pebbles and boulders.
Conifer : A cone bearing plant.
Constellation : An arrangement of stars visible in a particular region of the sky as viewed from Earth.
Continental rise : A wide area of sediment at the foot of the continental slope.
Continental shelf : A gently sloping underwater ledge that surrounds the coast of a continent.
Continental slope : A steep slope at the edge of the continental shelf down toward the ocean bottom.
Convection : The transfer of heat by the movement of molecules from warmer to cooler areas.
Core : The centre of the sun or Earth.
Coriolis force : A force due to the rotation of Earth that causes winds blowing toward the equator to curve to the west and winds blowing away from the equator to curve to the east.
Corolla : The petals of a Mower.
Corona : The outermost region of the sun′s atmosphere.
Cosmology : The study of the universe, including its beginnings.
Cotyledon : An embryo leaf.
Covalent bond : A chemical bond formed when two or more atoms share pairs of electrons, forming a molecule.
Creep : A type of erosion in which soil slowly moves down a slope.
Crest : The high point of a wave.
Cross-pollination : Fertilization that occurs when pollen from one flower reaches a pistil of another plant.
Crust : The rocky, outermost layer of Earth.
Crystal : A solid consisting of atoms or molecules arranged in a regular, three−dimensional pattern of flat surfaces and angles.
Cumulonimbus : A massive, tall cloud from which a thunderstorm may form.
Cumulus : A white or dark grey, puffy cloud that is rounded at the top and flat at the bottom.
Current : 1) A flow of electricity, especially the amount of electric charge passing a fixed point.
2) A large flow of ocean water at the surface or near the floor.
Current electricity : The continuous How of electric charges.
Cuticle : The waxy layer on some leaves.
Cutting : A method of vegetative propagation in which part of a plant is placed in water or moist soil to develop roots.
Cytoplasm : The substance within a cell but outside its nucleus in which many of the cell′s activities occur.
Dark matter : Hypothetical form of matter that does not send out or absorb electromagnetic radiation.
Daughter cell : One of two identical cells produced by mitosis.
Decay : 1) Verb: To change from the atom of one element info the atom of another element by emitting nuclear particles.
2) noun: The slowdown of a satellite due to air resistance.
Deciduous : Describing a tree that loses its leaves in winter.
Decomposer : An organism that feeds by breaking down dead plants and animals into nutrients.
Delta : A low fan−shaped plain at the mouth of a river formed by sediment carried and deposited by the river.
Deoxyribonucleic acid : A chain of molecules that carries hereditary information and directs the production of proteins. Also called DNA.
Dermis : The middle layer of the skin.
Dew point : The temperature at which the air cannot hold any more water vapour.
Diaphragm : A large, dome−shaped muscle that forms the door of the chest cavity.
Diarthrotic joint : A linkage between bones that allows free movement.
Dicotyledon : A flowering plant that grows from a seed with two cotyledons, such as most wood producing plants, fruit, and vegetables. Also called dicot.
Differentiate : To become specialized.
Diffraction : The bending or spreading of a wave around an obstacle
Direct current : An electric current that flows in one direction only. Also called DC.
Dispersion : The separation of light into different colours of the spectrum.
DNA : A chain of molecules that carries hereditary information and directs the production of proteins.
Doldrums : A calm, generally windless area near the equator.
Domain : A region in a substance in which the magnetic fields of the electrons are lined up. Polarizing the region.
Dome mountain : A mountain formed when molten rock rises under Earth′s surface but does not break through, causing a rounded swelling.
Dominant : Describing an allele whose effect overpowers that of the other allele in the pair.
Doppler effect : A change in the pitch of a sound when the source of the sound moves toward and then away from the listener, caused by the decrease in the frequency of the sound waves as the source recedes.
Doppler shift : The phenomenon that light reaching Earth from distant galaxies shifts toward the red end of the visible spectrum because its wavelength increases as the galaxies rapidly recede.
Dormancy : A period of inactivity.
Double helix : The twisted, ladder like form that the DNA molecule takes.
Double star : A star that appears in a pair
Drainage basin : A region from which water empties into a river system.
Ductile : Describing a metal that can be drawn out into a wire.
Dynamics : The branch of mechanics that describes bodies not in equilibrium because of forces acting on them.
Eclipse : The darkening of a heavenly body as it passes through the shadow of another body in space.
Eclipsing binary : One of a pair of stars whose light is periodically blocked from reaching Earth when the second star moves between it and Earth.
Ecosystem : All the living organisms and the nonliving physical environment in a particular area.
Electricity : A form of energy caused by the flow of electrons through substances.
Electrochemistry : The study of chemical reactions that involve electricity.
Electrolysis : A process in which an electric current is passed through a chemical solution to separate certain elements.
Electromagnetic radiation : Waves of energy made up of an electric and a magnetic field that travels through space at the speed of light.
Electron : A subatomic particle with a negative charge that orbits the nucleus of an atom.
Element : One of the simplest substances. An element cannot be separated into simpler parts by ordinary chemical means.
Elliptical galaxy : A galaxy that is round or shaped like a flattened globe.
Embryo : An early stage in the development of a plant or an animal.
Endangered : Describing a species that is at risk of extinction.
Endocrine gland : A gland that secretes a hormone into the blood.
Endoplasmic reticulum : A network of membranes in the cytoplasm of a cell that is involved in the manufacture and activity of proteins.
Endosperm : Food storage tissue in the seed of a flowering plant.
Energy : The ability to do work.
Enzyme : A protein molecule that speeds up chemical reactions in cells.
Epicentre : The point on the Earth′s surface directly above the focus of an earthquake.
Epidermis : 1) The outer layer of cells on a plant, including the upper and lower surfaces of the leaves.
2) The outermost layer of human skin.
Epiglottis : A plate of cartilage that closes the entrance to the trachea as a person eats so that food cannot enter.
Epiphyte : A plant that grows on another plant but draws nutrients from the air and rain.
Epkotyl : The upper part of a seedling, which grows to form the stem.
Equilibrium : The condition in which all forces acting on an object balance, cancelling each other out.
Erosion : The wearing away and moving of rock or other material.
Escape velocity : The minimum velocity necessary for an object to overcome the gravitational pull of Earth or another body.
Evaporation : The act of a heated liquid becoming a gas.
Evolution : The theory that species undergo changes in their inherited characteristics over time.
Excited : State, the condition of an atom when its electrons absorb energy and move to a higher energy level.
Exfoliation : A type of weathering in which rock layers are weakened and peeled away as a result of shifts in temperature.
Exocrine gland : A gland that secretes a substance into a duct.
Exoskeleton : A hard outside covering, such as a shell. Exosphere, the uppermost part of the atmosphere, which gradually fades into outer space.
Extinct : 1) Describing a species that has died out.
2) Describing a volcano that is no longer likely to erupt.
Extrusive : Describing igneous rock formed from magma forced onto Earth′s surface.
Fallopian tube : One of two narrow ducts that lead from the ovaries to the uterus in a human female.
Fault : A fracture in Earth′s rocky crust.
Fault-block mountain : A mountain formed when rock along a break in Earth′s crust is pushed upward.
Ferromagnetic : Describing a material in which the magnetic fields of the electrons do not cancel out each other, making the substance capable of becoming magnetic.
Fertilization : The union of a sperm with an egg.
Fibrous root : A system of many slender roots that spread out in all directions.
Filament : The long, narrow stalk that forms part of the stamen of a flower.
Fission, nuclear : A reaction in which a bombarding panicle splits a nucleus and releases Energy.
Flagella : Long, whip like tails or projections. Plural of flagellimi.
Flare : A relatively brief burst of light shooting out from the sun′s atmosphere.
Fluorescent : Glowing only while being exposed to extra energy.
Focus : The point under the surface at which rocks first break during an earthquake.
Fog : A cloud that hovers at or near the ground.
Fold mountain : A mountain formed when Earth′s crust moves, causing wrinkles or waves at the surface.
Foliated : Describing metamorphic rock that has visible layers or bands.
Food chain : The series of stages i.e., organisms that energy goes through in the form of food.
Food web : An overlapping network of food chains.
Force : A push or pull exerted on an object that has mass.
Forensic chemistry : A specialized field of analytical chemistry that aids in the detection of crime and the prosecution of criminal cases.
Fossil : The remains or imprint of a plant or an animal.
Fragmentation : A form of asexual reproduction in which the body of an organism breaks into two or more pieces and each piece develops into a new organism.
Frequency : The number of times that a regularly repeated event, such as the sound waves produced by a vibrating object, occurs in a given unit of time.
Friction : The resistance to motion of objects that touch.
Frond : The leaf of a fern.
Front : A zone where a cold air mass and a warm air mass meet.
Fungus : A member of the kingdom Fungi; an organism that feeds on decaying matter or living organisms and that reproduces by means of spores.
Fusion, nuclear : A reaction in which light−weight nuclei collide and fuse to produce the nucleus of a heavier element and a tremendous amount of energy.
Galactic cluster : An irregularly shaped group of stars.
Galaxy : An enormous system of stars, gas, and dust held together by gravity.
Gamete : A sex cell.
Gametophyte : The generation of a plant that produces gametes.
Gamma rays : A form of electromagnetic radiation that travels in short waves.
Gas : A state of matter in which molecules move about rapidly, with little attraction between them.
Gene : The section of a DNA molecule that helps determines a particular characteristic that an offspring may inherit from its parent.
Gene splicing : A process in which a gene sized fragment of DNA is isolated from one organism and joined to a DNA molecule from another organism.
Genetic fingerprinting : A technique used by forensic chemists to identify people by their DNA
Geotropism : Growth of a plant toward or away from gravity.
Germination : The sprouting of a seed.
Giant : A large, bright, but relatively cool star.
Giant planet : One of the four large planets − Jupiter, Saturn, Uranus, and Neptune − composed mostly of gases.
Gibberellins : Plant hormones that speeds seed germination and make plants grow and blossom.
Glacier : A large mass of slow moving ice.
Globular cluster : A large, ball−shaped group of stars.
Gluon : A subatomic particle that transmits a force that binds quarks together.
Glycolysis : The process by which a cell breaks down the sugar glucose, resulting in the raw material pyruvic acid and energy stored as ATP.
Gneiss : One of the oldest rocks on Earth, formed in Precambrian time.
Golgi body : A structure in the cytoplasm of a cell that stores and releases various products of cell activities.
Gradualism : The belief that evolutionary changes take place slowly over long periods of time.
Grafting : A method of vegetative propagation in which part of a plant is attached to another plant, which provides the root system and lower part of the new plant.
Granule : A ′bubble′ of gas on the sun′s surface that rises from the convection zone to the photosphere.
Gravitation : The force of attraction that exists among all bodies in the universe.
Graviton : A hypothetical subatomic particle that is thought to transmit gravity.
Gravity : The gravitational force that a specific object exerts on other bodies on or near it.
Greenhouse effect : The trapping of solar heat near a planet′s surface.
Gristle : The tough, elastic substance forming part of the skeleton of vertebrates.
Ground state : The condition of an atom when all its electrons are at their lowest possible energy level.
Gymnosperm : A plant that produces naked seeds, usually in cones.
Hadal zone : Deepest region of the ocean, where few organisms can live. Hadron, a subatomic particle formed when two quarks combine.
Half life : The length of time it takes for half the atoms of a radioactive substance to break down, or decay.
Halogen : One of the elements in group 7A of the periodic table, so called because they combine with metals to produce salts (halogen means salt producer).
Halophyte : A salt tolerant plant.
Head : The nucleus and coma of a comet.
Heat : Energy that is transferred between two objects because of a temperature difference between them.
Heat capacity : The amount of heat required to raise the temperature of 1 gram of a substance by 1° C.
Herbaceous : Describing a soft green plant stem.
Hermaphrodite : An animal having both male and female sex organs.
Heterozygous : Having two different alleles of the same gene.
Hibernate : To sleep through the winter.
High : An area with high atmospheric pressure.
High tide : A bulge of water on Earth′s surface produced by the gravity of the moon and sun. High tides occur at the same place about every 12 hours and 25 minutes.
Homologous : Corresponding; matching.
Homozygous : Having the same two alleles of the same gene.
Hormone : A chemical substance secreted by a gland that enters the bloodstream and affects the activity of an organ, tissue, or cell.
Horse latitudes : The area 30° north or south of the equator where air from the equator cools and sinks.
Humidity : The amount of water vapour in the air.
Humus : Decomposed organic matter in soil.
Hurricane : A huge, violent, whirling storm that develops over warm ocean waters. Also called typhoon or tropical cyclone.
Hydrocarbon : An organic compound that contains only hydrogen and carbon.
Hydrogen transport system : A series of reactions in a cell that produce water during cellular respiration.
Hydrophyte : An aquatic plant.
Hydrotropism : The growth of a plant toward or away from water, occurring mostly in roots and almost always toward water.
Hyphae : Threadlike filaments that form the main part of a fungus. Plural of kypha.
Hypocotyl : The lower part of a seedling, which becomes the plant′s primary root.
Hypothalamus : A part of the brain that links the nervous and endocrine control systems.
Igneous rock : Rock formed from magma.
Incubation : The act of keeping an egg or young animal warm.
Inertia : The tendency of an object to remain at rest or moving until a force acts on it.
Inferior vena cava : The large vein through which blood from the lower trunk and legs enters the heart.
Infrared ray : Radiant energy with a wavelength longer than that of red light in the visible spectrum but shorter than a microwave.
Infrasonic wave : A sound wave with a frequency below the range of human hearing.
Inorganic chemistry : The study of chemical substances that do not contain carbon.
Inorganic compound : A compound that does not contain carbon. Most compounds that do not contain living matter or the remains of living matter are inorganic.
Instinct : An inborn, unlearned behaviour.
Insulator : A substance in which the electrons are too firmly bound to their nuclei to permit electricity, heat, or sound to flow through.
Intensify : The amount of energy that passes each second through a given area perpendicular to the direction of a sound wave. Intensity relates to loudness.
Interference : The action of waves passing through the same point by which they reinforce or diminish each other.
Interstellar : Between or in the region of stars.
Interstitial fluid : A fluid that bathes and nourishes the cells of body tissues.
Intrusive : Describing igneous rock formed from magma below the Earth′s surface.
Invertebrate : An animal that has no backbone.
Involuntary muscle : Muscle that is found in an internal organ of the body.
Ion : An electrically charged atom or group of atoms.
Ionic bond : A chemical bond formed when one atom loses electrons to one or more other atoms, forming an ionic compound.
Ionization : A gain or loss of electrons that results in an atom becoming an ion.
Ionosphere : The region of the Earth′s atmosphere characterized by charged atoms and molecules.
Irregular galaxy : A galaxy with no defined shape.
Isomer : A substance that has the same type and number of atoms as another substance and yet is a different substance because of the arrangement of the atoms.
Isotope : One of two or more forms of the atom of an element that have the same number of protons but a different number of neutrons.
Jet stream : Swift winds flowing above the Earth′s surface that can change weather patterns.
Kinetic energy : The energy of movement.
Krebs cycle : A series of reactions in a cell in which pyruvic acid produced by glycolysis is used to create carbon dioxide, water, and energy stored as ATP. tricarboxylic acid cycle or the citric acid cycle.
Larva : An early stage of an animal in which it does not resemble an adult of the species.
Larynx : The voice box; the upper end of the trachea, where the vocal cords are.
Laser : A device that produces a very narrow, powerful beam of light.
Lateral bud : A bud that develops at a point where a leaf joins a stem.
Lava : Molten rock or magma, that reaches Earth′s surface,
Layering : A method of vegetative propagation in which a growing medium such as soil or sphagnum moss is placed around a part of the plant so that new roots develop and grow into it.
Lepton : A subatomic particle that may carry a negative charge or no charge.
Lichen : A fungus and algae living together.
Ligament : A strong tissue that connects bones.
Light-year : The distance a pulse of light travels in one year, about 9.46 trillion kilometers.
Lightday : The distance a pulse of light travels in one day, about 26 billion kilometers.
Linear motion : Movement along a line.
Lipid : A macromolecule, consisting primarily of carbon and hydrogen, that stores energy for living things, as well as forms the basic structure of cell membranes. Fats and oils are lipids.
Liquid : A state of matter in which molecules move about easily, but with some force that attracts them to one another.
Lithification : The process of rock formation.
Longitudinal wave : A sound wave in which the vibrations occur in the same direction that the wave travels.
Low : An area with low atmospheric pressure.
Low tide : The lowest level of water on Earth′s oceans and seas. Low tides occur halfway between high tides.
Luminescence : The glowing of an object when its electrons are excited by energy other than heat.
Lymph : Interstitial fluid that drains into lymphatic vessels, carrying wastes, dead cells, and bacteria with it.
Lysosome : A structure in the cytoplasm of a cell that helps break down substances.
Macromolecule : A large, complex molecule formed from simpler molecules linked together.
Macrophage : A cell that rids the blood of old or damaged cells as well as bacteria and other foreign substances.
Magma : Molten rock below Earth′s surface.
Magnetic field : The region in which the effects of a magnet can be felt.
Magnetism : A force produced by a moving electric charge, or by the motion of electrons in the atoms of certain materials, which are called magnets.
Magnetosphere : Part of Earth′ magnetic field, forming a mostly circular region in space surrounding the planet.
Magnitude : The brightness of a star.
Main-sequence star : One of a group of stars that show a specific relation between temperature, colour, brightness, and mass. About 90 per cent of stars seen from Earth are main sequence stars.
Malleable : Describing a metal that can be hammered into a thin sheet.
Mantle : The layer of Earth lying below the crust composed of hot, dense rock.
Maria : Vast, smooth plains on the surface of the moon. Plural of mare.
Marsupial : A mammal that carries its young in a pouch.
Mass : The amount of matter in an object.
Mass number : The sum of the protons and neutrons in an atom.
Mass spectrum : A pattern of peaks differing in height that is produced by a mass spectrometer when ions from a substance are separated by a magnetic field according to their mass and charge. A mass spectrum can be used to identify the substance,
Matter : The "stuff" things are made of, molecules and atoms.
Megagametophyte : The food storage tissue in the seed of a cone−bearing plant. Meiosis, cell division that results in four sex cells.
Mesosphere : The region of the atmosphere above the troposphere, about 50 to 80 kilometres above the Earth′s surface, where the air is thin and extremely cold.
Mesozoic Era : A period in Earth′s history that began about 240 million years ago and ended about 63 million years ago.
Metabolism : Biochemical processes that underlie all cellular activity.
Metal : A mineral that is shiny, reflects tight and is a good conductor of heal and electricity.
Metamorphic rock : Rock formed from preexisting rock that has changed in appearance and composition as a result of heat and pressure.
Metamorphosis : In animals, a gradual process of change in form from young to adult.
Meteor : A meteoroid that enters and burns in Earth′s atmosphere, visible from Earth′s surface.
Meteorite : A meteor that crashes into Earth′s surface.
Meteoroid : A small piece of metallic or stony matter that travels through the solar system.
Micro crater : A microscopically small crater on the surface of the moon, formed by the high speed impact of cosmic dust.
Microwave : A form of electromagnetic radiation with a relatively long wavelength.
Mid ocean ridge : A chain of mountains on the ocean floor formed where sections of the Earth′s oceanic crust have spread apart.
Migration : The journey of a large group of animals from one region to another.
Mineral : A natural, inorganic substance formed within the Earth having a characteristic chemical makeup.
Minor planet : A relatively small planetary body that revolves around the sun.
Mitochondria : The structures in the cytoplasm of a cell that produce energy. Plural of mitochondrion.
Mitosis : Cell division that results in two identical cells.
Mixture : A combination of substances in which the substances are not chemically changed.
Molecular mass : The total of all the atomic masses of the atoms in a molecule.
Molecule : One of the basic units of matter composed of atoms held together in certain arrangements. A molecule is the smallest particle into which a substance can be divided and still have the chemical identity of the substance.
Moneran : A member of the kingdom Monera; a primitive, one celled organism without a nucleus.
Monocotyledon : A flowering plant that grows from a seed with one cotyledon, including grasses and cereals. Also called monocot.
Monotreme : A mammal that lays eggs.
Moraine : The accumulation of rocks, soil, and other debris left by a glacier as it melts.
Mouth : The place where a river enters the sea.
Multiple stars : A group of Stars in which a pair of binary stars travels with another pair or with a single star.
Muon : A subatomic particle having a mass 207 times that of an electron.
Mutation : An evolutionary process that produces random variation in the genetic makeup of a species or population. It occurs when a mistake happens in the replication of genes in an individual.
Natural selection : An evolutionary process that determines which characteristics will endure, according to the degree to which they contribute to survival.
Neap tide : A lower than average high tide, caused when the moon′s tidal influence is partly neutralized because it is at right angles to the line of the sun and Earth.
Nebula : A large cloud of hydrogen gas, dust, and other material from which stars and planets are formed.
Negative ion : An atom that is negatively charged because it has gained electrons.
Nekton : The relatively large ocean animals that can swim freely.
Nephrort : A unit of the kidney that filters blood.
Neritic zone : Region of ocean water on the continental shelf, where most ocean organisms live.
Neuron : A nerve cell.
Neutron : A subatomic particle with no electrical charge, found in the nucleus of an atom.
Neutron star : A rotating, extremely dense core left after a supernova, in which the remaining matter has condensed to such a degree that atoms have broken up and protons and electrons have fused, leaving behind only neutrons.
Noble gas : One of the elements in group 8 A of the periodic table. Also called rare gas.
Node : 1) The point at which two sound waves cross and cancel each other′s vibrations.
2) The point where a leaf joins a stem.
Nonrenewable resource : A resource that cannot be replenished once it is used.
Nonvascular : Describing a plant that lacks tissue − xylem and phloem − to carry substances through the plant.
Notochord : A rod of cartilage that runs along the back, found in many lower vertebrates and the embryos of higher vertebrates.
Nova : An exploding star that blows off its surface layers, brightens suddenly and then returns to its original magnitude.
Nuclear fission : A reaction in which a bombarding particle splits at nucleus and releases energy.
Nuclear fusion : A reaction in which light weight nuclei collide and fuse to produce the nuclease of a heavier element and tremendous amount of energy.
Nucleic acid : A long chain of smaller molecules called nucleotides that stores and transmits the information necessary for producing proteins. DNA and RNA are the nucleic acids.
Nucleic base : One of four compounds − adenine, cytosine, guanine, and thymine − that help make up a DNA molecule.
Nucleolus : A small structure within the nucleus of a cell that contains the RNA necessary for making proteins.
Nucleus : 1) The centre of an atom, composed of protons and neutrons. 2) The part of a cell that controls the cell′s activities, separated from the cytoplasm by a nuclear membrane. 3) A part of a comet, composed of frozen gases, ice and dust. 4) The bulge in the centre of a spiral galaxy around which the spiral arms revolve.
Nymph : A stage in the development of an insect in which it largely resembles its parents but has no wings.
Oesophagus : A short, muscular tube that leads from the mouth to the stomach.
Ohm : A unit of measure of the resistance to an electric current.
Opaque : Describing a substance that blocks light.
Open cluster : An irregularly shaped group of stars. Also called galactic cluster.
Open universe theory : The scientific belief that the universe will continue expanding until it fades to nothing.
Orbital : A wavy path that an electron follows around the nucleus of an atom.
Orbital plane : An imaginary flat surface along which a planet revolves around the Sun.
Ore : A rock from which a mineral can be removed profitably.
Organelle : A specialized structure within the cytoplasm of a cell that is analogous in function to an organ in a higher animal.
Organic chemistry : The study of chemical substances that contain carbon.
Organic compound : A compound that contains carbon. Compounds that make up living things or the remains of living things are organic compounds.
Oscillating universe theory : The scientific belief that the universe will eventually start to contract until it collapses on itself, then start to expand again.
Oscillation : A repeated back−and−forth motion across a centre line or point. Also called vibration.
Osmosis : The crossing of water through a cell′s semi permeable membrane.
Ovary : The structure in a female animal or in the female part of a flower that contains egg cells.
Oviparous : Producing eggs that hatch outside the body.
Ovoviviparous : Producing eggs that hatch within the body but receive no nourishment from the mother.
Ovule : A structure in the ovary of a flower within which egg cells form.
Ovum : A female sex cell.
Oxidation : A chemical reaction in which a substance loses electrons.
Oxide : A compound of oxygen and another element. Many minerals consist of oxides.
Ozone (Oj) : A molecular form Of oxygen that occurs naturally in a protective layer high in the atmosphere but that also may be produced near ground level when compounds in vehicle exhaust react with sunlight, forming smog.
Palaeozoic Era : An early period in Earth′s history that began about 570 million years ago and ended about 240 million years ago.
Palisade cell : A cell in a leaf blade that contains chloroplasts.
Panfhalassa : The world′s single ocean that existed during (he Palaeozoic Era and surrounded Pangaea.
Pangaea : A single continent that existed during the Palaeozoic Era and included all the land masses of the Earth.
Panspermia : The theory that life on Earth began when spores from some other part of the universe landed on the planet and began to develop.
Parabolic motion : Movement that follows a symmetrical, arched curve.
Parasite : An organism that lives and feeds on another organism.
Parsec : A unit of distance equal to 3.26 lightyears, or 30.9 trillion kilometres.
Pathogen : A disease causing microorganism.
Penis : The male sex organ, through which sperm leave the body.
Penumbra : A partial shadow caused by the bending of some light around the edge of an opaque object.
Period : 1) A horizontal row in the table of elements, or periodic table.
2) The time it takes for a pulsating star to go through one complete cycle of brightness and darkness.
Periodic table : A table that displays the elements in order of their atomic numbers, with chemically related elements in vertical columns.
Petiole : The thin stalk that grows between a stem and the base of a leaf blade.
Pharynx : The cavity behind the nose and mouth.
Phase : One stage in the changing appearance of the shape of the moon as seen from Earth.
Phloem : Plant tissue that carries food produced in the leaves to other parts of the plant.
Phosphorescent : Glowing long after receiving extra energy.
Photochemistry : The study of chemical reactions that result when molecules absorb light.
Photoelectric effect : A metal′s emission of electrons when struck by electromagnetic radiation.
Photon : A particle of light energy that also behaves like a wave.
Photosphere : The Sun′s surface and innermost layer of its atmosphere.
Photosynthesis : The process by which green plants use water, carbon dioxide, and the energy of sunlight to make food in the form of organic molecules.
Phototropism : The growth of a plant toward or away from light.
Physical change : A process in which a substance changes in appearance but not in chemical nature.
Physical chemistry : The study of the general rules and principles that govern the chemical and physical properties of matter.
Phytoplankton : Tiny plantlike organisms that float in the ocean.
Pistil : The female reproductive organ of a flower.
Pitch : The highness or lowness of a sound, determined by its frequency.
Pituitary gland : The ′master gland′ that releases hormones that regulate other endocrine glands.
Placenta : The structure that, in most mammals, attaches a fetus to the mother and provides nourishment.
Planet : A dark, solid or gaseous body that orbits the sun or another star.
Plankton : The highness or lowness of a sound, determined by its frequency.
Plasma : 1) The liquid portion of blood.
2) An electrically charged gas.
Plasma membrane : The extremely thin covering of a cell.
Plasmid : A DNA molecule in the cytoplasm of a bacterium that is joined to DNA from another source during genetic engineering.
Plate : One of the large pieces of rock that, according to the theory of plate tectonics, makes up Earth′s crust and moves on the hot, flowing rock below the upper mantle.
Plateau : A broad, relatively flat, high region.
Platelet : A disc like structure in the blood that helps seal wounds.
Plumule : The bud that produces the first leaves of a plant.
Polar easterlies : Cold winds coming from the poles that blow from the east toward the regions 60° north and south of the equator.
Polar molecule : A molecule in which more positive charge collects at one place and more negative charge collects in another.
Pollen grain : A structure formed in the anther of a flower that produces sperm.
Pollen tube : A tube that develops when a pollen grain reaches the stigma of a flower, growing down the style to an ovule in the ovary.
Pollination : The transfer of a pollen grain from an anther to a stigma, resulting in fertilization.
Polymer : A large molecule formed through the linking of many smaller molecules.
Polypeptide : A molecular chain of amino acids that makes up a protein.
Population : A group of individuals of the same species living in the same area.
Positive ion : An atom that is positively charged because it has lost electrons.
Potential energy : Stored energy.
Power : The rate at which work is done, equal to the amount of work done divided by the lime taken to do it.
Pressure : The amount of force per unit of area.
Prevailing westerlies : Winds from the west that blow between 30° and 60° north and south of the equator.
Primary consumer : A plant eating animal.
Primary producer : A green plant, which produces food through photosynthesis.
Primordial fireball : The rapidly expanding region of radiation following the big bang.
Product : The result of a chemical reaction.
Proltaryote : A cell that lacks a nucleus.
Prominence : A shining arc of gas that rises from the Sun.
Protein : A macromolecule consisting of carbon, hydrogen, nitrogen and oxygen that is used to build cell tissue or carry out chemical reactions in living things.
Protist : A member of the kingdom Protista: generally a one-celled organism with a nucleus that may have plantlike or animal like characteristics.
Protocell : An early, nonliving form, consisting of macromolecules within a protective membrane, that some scientists propose was a stage in the chemical evolution of life on Earth.
Protogalaxy : An early form of a galaxy.
Proton : A subatomic particle with a positive charge found in the nucleus of an atom.
Protostar : A region of hydrogen gas, dust, and other material of fairly stable high density and temperature that will develop into a star.
Pseudopod : A ′false foot′, formed by certain one−celled organisms that project part of their membrane and cytoplasm out to capture food or move.
Pulsar : A rapidly spinning neutron star with a powerful magnetic field that regularly emits bursts of electromagnetic radiation.
Pulsating variable : A star that varies in brightness, expanding as it brightens and contracting as it dims.
Punctuated equilibrium : The theory that a new species might evolve rapidly in geographic isolation and invade the territory of the parent species, which then would become extinct.
Pupa : A stage in the life of an insect during which it develops from a larva to an adult.
Qualitative analysis : As part of analytical chemistry, a test of a substance to see what types of elements or compounds are present.
Quantitative analysis : As part of analytical chemistry, a test of a substance to measure the amounts of different chemicals in it.
Quantum : A small, discrete packet of energy.
Quark : An extremely tiny panicle of matter that makes up protons and neutrons.
Quasar : A relatively small, very bright object that lies at ihe centre of certain distant galaxies.
Radial symmetry : Having like parts arranged around a central point.
Radiation : Energy that is emitted as waves or particles.
Radiation belt : A zone of electrically charged particles in Earth′s magnetosphere.
Radio galaxy : A galaxy, usually elliptical, that emits strong radio waves.
Radio wave : An electromagnetic wave with a long wavelength.
Radioactive : Describing an element that naturally emits radiation.
Radioisotope : A radioactive isotope.
Rare earth element : A member of the lanthanides, a group of elements so called because they were once considered very rare.
Rare gas : One of the elements in group 8A of the periodic table. Also called noble gas.
Reactant : A substance that undergoes a chemical change during a chemical reaction.
Receptacle : The point at which a flower is attached to a stem.
Recessive : Describing an allele whose effect is overpowered by that of the other allele in the pair.
Recombinant DNA : A hybrid DNA molecule formed by gene splicing, combining genetic material from different types of organisms or cells.
Red giant : A large, bright, relatively cool star that glows red.
Red shift : The phenomenon that light reaching Earth from distant galaxies shifts toward the red end of the visible spectrum because its wavelength increases as the galaxies rapidly recede. Also called Doppler shift.
Redox process : The combined transfer of electrons in which one substance loses electrons (oxidation) and another substance gains them (reduction).
Reduction : A chemical reaction in which a substance gains electrons.
Refraction : The change in direction of a wave when it moves from one medium to another.
Regeneration : The replacement or regrowth of a missing part of a plant or animal.
Relative humidify : The amount of water vapour in the air compared with the total amount of vapour the air could hold at that particular temperature.
Renewable resource : A resource that can be replenished or that will not run out.
Resonance : A phenomenon that occurs when one object is made to vibrate at its own natural frequency by impulses received from a second object vibrating at the same frequency.
Rhizoid : A root like growth of fungi or plants such as liverworts, mosses and hornworts.
Ribonucleic acid : A chain of molecules that helps in the production of proteins. Also called RNA.
Ribosome : A structure in the cytoplasm of a cell, consisting largely of RNA, that makes proteins.
Rille : A long, narrow valley on the moon.
RNA : A chain of molecules that help in the production of proteins.
Rotation period : The length of time it takes a planet to rotate once on its axis; its day.
Rotational axis : An imaginary line drawn through the centre of a planet around which the planet rotates.
Runner : A long, thin stem sent out from certain plants that grows along the surface of the soil, producing leaves and stems that may become new plants if separated from the parent plant.
Salinity : A measure of saltiness; specifically, the number of grams of salt in 1,000 grams of water.
Saprophyte : An organism that lives and feeds on decaying matter.
Saturated : Describing the air when it is holding as much water vapour as it can at its temperature, having a relative humidity of 100 per cent.
Savanna : A grassland with widely spaced trees found in certain regions of the world.
Schist : A metamorphic rock and one of the oldest rocks on Earth, formed during Pre−cambrian time.
Scientific creationism : The belief that the world and all species in it began with a single act of creation.
Scrotum : An external sac that holds the testicles.
Sea−floor spreading : The process by which two oceanic plates separate, allowing magma to flow up and fill the opening in the ocean floor, forming new crust.
Secondary consumer : An animal that eats plant eating animals.
Sedimentary rock : Rock formed when organic and inorganic material is deposited and pressed into layers.
Seed coat : The outer part of a seed that protects the embryo.
Seismic wave : A vibration in rock caused by an Earthquake.
Self-pollination : Fertilization that occurs when pollen from one flower reaches a pistil on the same plant.
Semiconductor : A substance that transmits electricity, heat, or other energy in a predictable manner.
Sepal : A green leaf like structure that helps form the calyx around the bud of a flower.
Sexual reproduction : Reproduction in which a male sperm cell joins with a female egg cell to produce a new organism.
Shale : A type of sedimentary rock made of compressed, cemented particles of clay.
Shell : An electron′s orbit around the nucleus of an atom.
Silicate : One of a group of minerals that combine oxygen, silicon, and one or more metals and that make up about 95 per cent of all the minerals in Earth′s crust.
Skeletal muscle : Muscle that is attached to bone and that enables movement. Also called voluntary muscle.
Smooth muscle : Muscle that is found in an internal organ of the body. Also called involuntary muscle.
Solar cosmic ray : Fast moving atomic nuclei and electrons emitted from the sun.
Solar storm : Especially violent activity on the sun′s surface or in its atmosphere.
Solar system : The Sun and all the objects that revolve around it.
Solar wind : Gases from the sun that expand outward toward the edge of the solar system.
Solid : A state of matter in which molecules vibrate but do not escape because the forces that attract and repel them are balanced.
Solubility : The ability of a substance to dissolve in another.
Solute : A substance that is dissolved in another.
Solution : A mixture of different substances that cannot be separated by mechanical means, such as filtration. A solution generally appears as one substance.
Solvent : A substance that dissolves another.
Spawning : A type of external fertilization in which the female releases eggs and the male covers them with sperm.
Sperm : A male sex cell.
Spermatophyte : A seed plant.
Spindle : The network of fibres extending across a cell along which chromatids move during cell mitosis.
Spiral galaxy : A galaxy shaped like a disc with a bulge in the centre, surrounded by curved arms that extend from the centre and rotate around it.
Spirilla : Spiral−shaped bacteria. Plural of spirillum.
Spirochaete : A spiral−shaped bacterium.
Spit : A ridge built out from an ocean shore, formed by waves depositing sand and other debris.
Spongy cell : A cell in a leaf blade that contains chloroplasts.
Sporangium : The structure of a fungus or plant in which spores are produced.
Spore : A reproductive structure of fungi and of some plants that may develop into a fungus or plant.
Sporophyte : The generation of a plant that produces spores.
Spring tide : A higher than average high tide, caused when the tidal influences of the moon and the Sun are combined because the moon, the sun, and Earth are in a straight line.
Stable : 1) Describing an atom that has the maximum number of electrons in its outermost shell.
2) Describing the nucleus of an atom in which the protons are electrically balanced by the neutrons.
Stamen : The male reproductive organ of a flower.
Standing wave : A wave produced when one wave and its reflection combine and form a pattern that appears to be standing still.
Star cloud : The largest grouping of stars in a galaxy.
Static electricity : A stationary electric charge that may be acquired when one substance rubs against another, causing a transfer of electrons.
Statics : The branch of mechanics that deals with objects at rest or moving at a constant speed in a constant direction.
Stigma : A flattened structure at the top of the pistil of a flower that receives pollen.
Stipule : A leaflikc structure that grows where a leaf′s petiole joins the stem.
Stomata : Tiny openings in the epidermis of a leaf through which substances pass. Plural of stoma.
Stratosphere : The region of the atmosphere between the troposphere and mesosphere, reaching to about 48 kilometres above the Earth′s surface, where the protective ozone layer lies.
Stratus : A smooth, flat cloud, lying close to the Earth, from which drizzle often falls.
Striation : A crossband in the fibre of a skeletal muscle.
Strong nuclear force : The force that holds the protons and neutrons within a nucleus.
Style : A tube in the middle of the pistil of a flower down which a pollen tube may grow.
Subcutaneous : Under the skin.
Subduction : The pushing of the edge of one of the Earth′s crustal plates under another, so that the edge sinks and is absorbed into the mantle.
Sublimation : The act of a solid passing directly into a gaseous state without first melting.
Sublittoral zone : The submerged land of the continental shelf, dominated by sea stars, brittle stars, and sea lilies.
Sunspot : relatively dark, cool patch that moves across the surface of the Sun.
Super cluster : A large galactic grouping that contains smaller groups of galaxies.
Super fluid : A liquid cooled to a temperature at which it has almost no viscosity.
Superconductivity : The ability of certain materials to conduct electricity with no resistance at temperatures near absolute zero.
Supercooled liquid : A liquid that falls below its normal freezing temperature without forming a solid.
Supergiant : One of the largest, brightest stars.
Superior vena cava : The large vein through which blood from the head and upper body enters the heart.
Supernova : A violent explosion of an entire star that ejects an enormous, fast moving cloud of matter into space and emits very bright light for a period of time.
Surface chemistry : A field of physical chemistry that studies the surface properties of compounds.
Surface tension : The force that pulls the molecules on the surface of a liquid toward those in the body of the liquid, forming a ′skin′ and preventing the liquid from flying apart.
Suspension : A mixture of different substances that can be separated by mechanical means such as filtration. A suspension often appears as a combination of two or more substances.
Synarthrodial joint : A connection between bones that allows little or no movement.
Tableland : A small plateau.
Taiga : A biome characterized by swampy, coniferous, evergreen forest land with long, cold winters. Also called boreal forest.
Tail : The part of a comet that extends away from the Sun.
Taproot : A plant system with one large root that grows down.
Tau : A subatomic particle having a mass about 3,490 times that of an electron.
Teleost : A fish with a bony skeleton.
Temperature : A measure of the kinetic energy of a substance′s molecules.
Tendon : A tissue connecting a muscle to a bone.
Terminal bud : A bud that forms at the end of a branch.
Terminal velocity : The maximum velocity a falling object can attain before resistance of the medium through which it is falling balances the force of gravity.
Terrestrial planet : One of the four planets closest lo the Sun − Mercury, Venus, Earth, and Mars − which are composed mostly of rock and have hard surfaces.
Testicle : One of the two glands that produce sperm in males.
Thermocline : Region of ocean water in which the temperature drops suddenly.
Thermosphere : The region of the atmosphere extending from an altitude of about 80 to 1,600 kilometres above the Earth′s surface, characterized by sparse gases and increasing temperatures.
Thigmotropism : The bending of a plant toward or away from contact or touch.
Timbre : Sound quality produced by overtones, or standing waves.
Tornado : A violent, funnel-shaped storm in which wind speeds may be more than 320 kph.
Trachea : The windpipe, which carries air from the nose or mouth to the lungs.
Trade winds : Winds that blow out of the east toward the equator from about 30° latitude north and south.
Transcription : The process by which a DNA code for the building of a particular protein is copied by RNA.
Transform fault : A crack in the Earth′s crust at the boundary of two plates sliding horizontally against each other.
Transformation : A change that a radioactive atom undergoes when its nucleus throws off excess protons and neutrons in an attempt to reach a stable condition. The atom then changes into the atom of another element.
Transition metal : One of a group of elements in columns 4B, 5B. 6B, 7B, and 8B of the periodic table that tend to act as catalysts.
Translation : The process by which RNA directs the sequence of amino acids in the production of proteins.
Translational motion : Movement along a line. Also called linear motion.
Translucent : Allowing light to pass through but scattering it.
Transmutation : A change that a radioactive atom undergoes when its nucleus throws off excess protons and neutrons in an attempt to reach a stable condition. The atom then changes into the atom of another element. Also called transformation.
Transparent : Allowing light to pass through without distortion.
Transpiration : A process whereby a plant gives off water through the stomata in its leaves.
Transverse wave : A wave in which the vibrations occur at right angles to the direction in which the wave is travelling.
Trench : A deep valley in the ocean door formed where sections of the Earth′s oceanic crust have moved together.
Tropical cyclone : A huge, violent, whirling storm that develops over warm ocean waters. Also called typhoon or hurricane.
Tropism : The growth or bending of a plant in response to stimulus.
Troposphere : The lowest layer of the atmosphere, extending 10 to 16 kilometres above the Earth′s surface and containing most of the atmosphere′s gases and almost all the dust and water vapour.
Tsunami : A huge wave caused by an eart−quake under the ocean.
Tundra : A biome mat has a cold, dry climate and cannot support trees.
Typhoon : A huge, violent, whirling storm that develops over warm ocean waters. Also called tropical cyclone or hurricane.
Ultrasonic wave : A sound wave with a frequency above the range of human hearing.
Ultraviolet rays : A form of electromagnetic radiation that travels in waves shorter than those of visible light.
Umbra : A completely dark shadow caused by the total blocking of light by an opaque object.
Unfoliated : Describing metamorphic rock that has no visible layers.
Unicellular : One−celled.
Unstable : 1) Describing an atom that does not have the maximum number of electrons in its outermost shell.
2) Describing the nucleus of an atom in which the neutrons are unable to counteract the positive forces between the protons. Such an atom is radioactive.
Urethra : The tube through which urine leaves the body.
Uterus : An organ in a female mammal in which a fetus develops and grows.
Vacuole : A fluid filled sac found in the cytoplasm of cells that may serve various functions.
Vagina : The birth canal in females, which extends from the uterus to the outside of the body.
Valency : The capacity of an atom to combine with another atom.
Van Allen belt : A zone of electrically charged particles in Earth′s magnetosphere.
Van der Waals forces : The relatively weak forces of attraction that hold molecules together, as opposed to the stronger forces that hold atoms together.
Vapour : The gaseous state of a substance below its critical temperature that can be liquefied if pressure is increased.
Vascular : Describing a plant that has tissue − xylem and phloem to carry substances through the plant.
Vegetative propagation : A type of asexual reproduction that produces a new plant from part of another plant.
Vein : A blood vessel that carries blood to the heart.
Velocity : The rate of motion in a particular direction.
Vent : The opening of a volcano.
Ventricle : A lower chamber of the heart.
Venule : A small vein that carries blood from capillaries to a larger vein.
Vertebrate : An animal with a backbone.
Visible spectrum : Electromagnetic radiation visible to the human eye.
Viviparous : Giving birth to live young that have developed within the mother.
Volcanic mountain : A mountain formed when molten rock erupts onto the Earth′s surface.
Voluntary muscle : Muscle that is attached to bone and that enables movement.
Vott : A unit of measure of the force of an electric current.
Warm-blooded : Having blood that always stays about the same temperature
Water table : The top of the underground zone where the rock is saturated with water.
Wavelength : The distance between one peak of a wave and the next peak.
Weathering : The breaking down of rock through chemical or physical means.
Weight : The force exerted on a mass by the gravity of a particular planet.
White dwarf : A small, extremely dense star that is dying.
X rays : A form of electromagnetic radiation that travels in waves shorter than those of ultraviolet rays but longer than those of gamma rays.
Xerophytic : Resistant to drought.
Xylem : Tissue that carries water and minerals from the roots to the other parts of a plant.
Zoology : The branch of biology that deals with the study of animals.
Zooplankton : Tiny animals that float in ocean water.
Zygote : A fertilized egg, which has all the information necessary for the development of a human being.
 
 
 
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