| air |
the mixture of gases that surrounds the earth. Air is made up of oxygen, nitrogen, and other gases, and has no taste, odor, or color. [1/6 definitions] |
| alien |
from a planet other than Earth; extraterrestrial. [1/5 definitions] |
| altitude |
the height of a thing above earth or above sea level. |
| anthill |
a pile of earth made by ants as they dig their underground nest. Anthills are found near the nest entrance. |
| Arctic Circle |
an imaginary line drawn around the earth parallel to the equator which marks the boundary of the Arctic. North of this line there are periods of continuous night in the winter and continuous day in the summer. |
| astronomer |
a scientist who studies the universe beyond the earth. |
| astronomy |
the branch of science that studies the universe beyond the earth. |
| atmosphere |
the gases surrounding the earth or other similar objects in outer space. [1/3 definitions] |
| atmospheric |
of, relating to, or made of the gases that surround the earth. |
| bacteria |
microscopic organisms that often play a role in the decay of living things, the process of fermentation, and sometimes in causing disease. Bacteria are each made up of only one cell, but different kinds of bacteria can take different shapes. These organisms live in all parts of the earth including oceans, deserts, glaciers, hot springs, and in the bodies of most living things. While some kinds of bacteria are dangerous, most kinds are useful because they help in the digestion of food, in the making of soil, in the creation of medicines, and in many other natural processes. |
| bacterium |
singular form of "bacteria." Bacteria are tiny living things made up of one cell each. Bacteria live in most living things and in all parts of the earth. Most bacteria are useful to people, but some are harmful because they can cause disease. |
| biodiversity |
the condition of having a wide variety of living things. If an area on the earth has biodiversity, it means that there are many different kinds of animals and plants living there. |
| bog |
an area of soft, wet earth; marsh. [1/2 definitions] |
| border |
a strip of earth planted with flowers or bushes. [1/5 definitions] |
| burrow |
to dig into or in the earth. [1/3 definitions] |
| canopy |
something high in the air or sky that is spread out over the earth. The top layer of branches and leaves in a rainforest, for example, is called a canopy. [1/2 definitions] |
| cave |
a natural hole or hollow in the earth. Many caves have openings in a hillside or cliff. |
| clay |
moist, stiff earth that is used for making brick, pottery, and tile. |
| cliff |
a high, steep face of rock or earth. |
| clod |
a lump of earth or clay. [1/2 definitions] |
| coal |
a hard black or dark brown substance that is found in the earth and burned as fuel. [1/2 definitions] |