Main->Readings->4th Grade Readings->Glossary
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
| absolute zero | The state in which molecules of matter are not moving at all. Though scientists have come very close to cooling matter that far, they cannot reach it. The temperature at which matter would reach absolute zero is -273° Celsius (or 0° Kelvin). |
| acceleration | A change in velocity. When something gets faster, it accelerates. |
| anatomy | The study of the way living things are put together and what the parts are. |
| angiosperms | Another name for flowering plants, plants which make their seeds in flowers. |
| animal | A many-celled living thing that can move (at least part of its life) and must eat other living or once-living things. |
| atom | The smallest particle of matter that can exist. |
| ballistics | The study of objects moving through the air or moving through space, or projectiles. |
| barb | Thin parts of the feather attached to the shaft. They form the vane, or fan, of the feather. |
| blade | The thin flat wide part of a leaf. |
| boiling point | The temperature at which a liquid turns into a gas. Each kind of matter has its own boiling point. |
| bolus | The soft wet ball of food made after the mouth has chewed and moistened it. |
| botanist | A scientist who studies plants. |
| botany | The study of plants. |
| calorie | A food calorie is the amount of heat needed to raise the temperature of one gram of water one degree Celsius. Scientists who study food use this unit to tell how much energy there is in food. |
| carbohydrate | Foods which provide energy. They are often called starches and sugars, and are found in things like bread, pasta, fruit, and cereal. |
| carbon dioxide | A gas which animals give off when they breathe. Unlike plants, animals take in oxygen and release carbon dioxide. |
| cell | The basic part of every living thing on earth. |
| cellulose | The fiber in plants which human beings do not digest (though cows and rabbits can). |
| chemist | A scientist who studies matter. |
| chlorophyll | The chemical in plants which traps the energy of sunlight so plants can make food. |
| cholesterol | A waxy substance made by the body and found in meats, eggs, and other foods. Your body needs some of it, but too much is bad for you. |
| classification | Sorting things into groups with similar traits. |
| cold-blooded | A vertebrate animal is cold-blooded if its temperature changes with the outside temperature. |
| condensation | Gas changing phase to a liquid. The water on the outside of a cold glass is condensation, and so is the mist above a pot of boiling water. |
| contact force | A force which is applied by an object touching another object. |
| crocodilian | A member of the reptile group which includes crocodiles and alligators. |
| deceleration | Slowing down. An acceleration in which the velocity gets slower. |
| density | The amount of matter packed into a given space. |
| digestion | Changing food into a form the body can use. |
| evolution | Change in living things over very long periods of time, and the development of new species from older species. |
| energy | The ability to do work. |
| entropy | The production of heat in every energy change. The gradual "winding down" of the universe. The amount of disorder and randomness in a system. |
| enzyme | Substances made by the body which help changes happen. Example: pepsin, which helps digest protein in the stomach. |
| esophagus | A muscular tube that goes down your throat to your stomach. |
| feather | Body covering of birds, important for flight and warmth, and similar to hair and scales. Like hair and scales, they are made from a substance called keratin and grow from the skin. |
| fat | A food type which helps the body by storing energy, and helping make cells. Fats are found in animal fat and vegetable oils. |
| fertilization | The process which happens when male and female cells join to start a seed. |
| field force | Force which act on objects without touching them. Examples are magnetism, gravity, the electrical force, and the force which holds atoms together. |
| fin | A fan-like body part in ray-finned fish. It has spines covered with a thin skin. The fish uses it to move. |
| fibrous root system | A plant root system in which there are several main roots with many smaller branching roots. |
| flower | The part of a plant where seeds are made. |
| force | A push or a pull on an object caused by another object. A force may cause an object to move faster or slower, start moving or stop moving, or change directions. |
| gas | A gas is matter with no definite shape and no definite volume. It spreads out and fills whatever container it is in. The molecules in gas move around freely and can get very far from one another. |
| gills | Thin sheet-like parts inside the body which allow water-dwelling animals to breathe under water. |
| graduate | A container marked with exact units of volume. Used for measuring the volume of liquids and powders. |
| gram | A unit of measurement in the metric system. The gram (g) measures mass, and is about the weight of a cubic centimeter of water. |
| gravity | A field force between objects made of matter which attracts the objects. |
| green stem | A type of stem which is thin, green, bends easily, and does not get thicker as the plant grows older. |
| gymnosperms | Plants which produce seeds in cones. Example: conifer |
| heat | Heat is the energy of moving molecules. |
| hydrochloric acid | An acid produced in the stomach which helps the body digest food. |
| hypothesis | A guess, made for the purpose of testing an idea. |
| inertia | Matter's tendency to resist changes in motion. Another name for inertia is mass! |
| kinetic energy | The energy of a moving object. |
| kingdoms | The five large groups into which scientists have classified all living things. (Currently, scientists are discussing whether there ought to be seven kingdoms instead.) |
| life cycle | All the stages in an animal's life, from egg to adult |
| liquid | A liquid is matter with no definite shape and a definite volume. A liquid takes the shape of its container. In a liquid, the molecules move and slide around each other. |
| liter | A unit of measurement in the metric system. A liter (L) measures volume, and is about equal to the volume of water in a cube 10 centimeters on every side. |
| lungs | Organs which allow animals to get oxygen from air |
| marsupial | A marsupial is a mammal which carries its young in a pouch after a short time in the uterus. |
| mass | The amount of matter in something. Mass can be measured with a balance. |
| matter | Anything which takes up space and has mass. Matter is made of atoms. |
| melting point | The temperature at which a solid changes to a liquid. Every kind of matter has its own melting point. |
| metamorphosis | An extreme change in body form from one life stage to the next, as with caterpillar to butterfly or tadpole to frog. |
| meter | A unit of measurement in the metric system. It was first set by the French to be equal to 1/10,000,000 (one ten-millionth) of the distance from the equator to the North Pole. Tthe meter is now defined as that distance which makes the speed of light in a vacuum equal to exactly 299,792,458 meters per second. |
| metric system | A system of measurement started by the French in 1790. In this system, there is only one unit of measurement for each quantity, larger and smaller units are created by adding prefixes to the basic unit, and the basic units are rational and related to each other. |
| molecule | A very small particle of matter. (In Part 4 of Unit 4, Matter: A molecule is a grouping of atoms). Molecules are made of atoms held together by one kind of chemical bond. |
| momentum | The combination of an object's mass and its velocity. A massive object going at a high velocity has a large momentum. |
| monotreme | A group of mammals which lays eggs. The only living members of this group are duck-billed platypuses and spiny anteaters (echidnas). |
| non-seed plants | Plants which produce new plants without seeds. |
| nutrient | Foods and other substances we need for the body to work right. Examples are carbohydrates, proteins, fats, water, vitamins, and minerals. |
| operculum | A bony flap covering the gills of fish. |
| organ | Two or more tissues working together to do a job for the body. Examples: bone, brain, and stomach. |
| organ system | Organs working together to do a job for the body. Examples: skeletal system, digestive system. |
| ovary | The part of the flower which contains the ovules and grows into a fruit. |
| ovules | The female cells of a plant. |
| oxygen | A gas which makes up a big part of the air around us. All animals must breathe oxygen. |
| parasite | Any organism which lives on another living thing and harms it. |
| peristalsis | A wave-like squeezing motion in a tube. Food moves down the esophagus by peristalsis. A mouse moves through a boa constrictor by peristalsis. |
| physicist | A scientist who studies the ways matter and energy act. |
| placental | A placental mammal is one which carries its young in the uterus until it is ready to be born. Most mammals are placental mammals. |
| phloem | The tubes which carry food in a plant's stem. |
| photosynthesis | The process by which plants make food. |
| pistil | The female part of a flower, which contains the ovaries and ovules. |
| pollination | The process of moving pollen from stamen to pistil. |
| potential energy | Stored energy of an object. Examples: gravitational potential energy, chemical potential energy, elastic potential energy. |
| power | The rate at which work is done. An engine is more powerful if it does a job in less time. |
| prefix | A prefix is a group of letters at the front of a word which changes the meaning of the word. |
| projectile | An object which shoots through the air (or through space). |
| property | Something which describes matter. A trait of matter. Examples: color, density, shape, texture, etc. |
| protein | Food which is a building block for cells. It is found in foods like meat, eggs, and beans like lentils |
| quill | The hollow part of a feather, at the base. The quill attaches to the bird's skin. |
| saturated fat | Fat which is a solid at room temperature. It is worse for your health than fats which are liquid at room temperature. |
| seed plants | Plants which produce new plants in seeds. |
| shaft | The solid part in the center of a feather, in the part nearest to the tip. The quills are attached to this part. |
| sodium | A mineral found in salt and other foods. Too much can be bad for blood pressure. |
| A solid is matter with a definite shape and a definite volume. The molecules in a solid vibrate in place. | |
| specialized | Something which does only one job. |
| species | A group of living things that is very closely related and can interbreed. |
| spore | A single cell which can grow into a new organism. Used by fungi and some plants for reproduction, instead of seeds. |
| stalk | The large central stem of a leaf. |
| stamen | The male part of a flower, which holds the pollen grains. |
| stomates | Holes in a leaf's underside which take in and release air. |
| taproot system | A plant root system in which a single large root grows straight down. |
| theory | In science, a theory is a good explanation for the facts. Theories are not beliefs, and they are not suggestions, but strong ways of explaining things. An example is the theory that the Earth revolves around the Sun. |
| tissue | A group of cells which does a single job. |
| vector | An arrow which shows direction and speed at the same time. |
| vein | Tubes which carry water or food in the leaf. |
| velocity | The speed of an object and the direction in which it is moving. |
| vibrate | To vibrate is to move back and forth very quickly, or wiggle. Heated molecules vibrate more. |
| volume | The amount of space something takes up. When you talk about something being big, or small, or 2 liters, or 3 cubic centimeters, you are talking about its volume. |
| warm-blooded | A vertebrate animal is warm-blooded if it keeps its temperature the same no matter what the temperature is outside it. |
| weight | A measure of how hard gravity is pulling on mass. Your mass stays the same, but gravity pulls on you less on the Moon, so your weight would be less there. |
| woody stem | A type of stem which is stiff and does not bend easily. It continues to get larger and thicker. |
| work | What is done when a force moves an object. No matter how much force is used, no work is done if the object does not move. |
| xylem | The tubes which carry water in a plant's stem. |
| zoologist | A scientist who studies animals. |
This page last updated August 15, 2002