| actinium |
a radioactive chemical element of the rare-earth group that has eighty-nine protons in each nucleus. (symbol: Ac) |
| Afro-Eurasia |
the land mass of Earth that includes all of Africa, Europe, and Asia. |
| agro- |
soil; earth; field. |
| alt.2 |
abbreviation of "altitude," the height of a given object or location above a specified base, such as sea level or earth, esp. the angular distance of a celestial body, measured from the horizon. |
| altitude |
the height of a given object or location above a specified base, such as sea level or earth. [1/4 definitions] |
| Antarctic Circle |
an imaginary line drawn around the earth parallel to the equator and north of the South Pole. |
| antipodes |
places directly opposite each other on the surface of the earth, as the North Pole and the South Pole. |
| apogee |
the point in the orbit of the moon or of a man-made satellite that is farthest from the earth. (Cf. perigee.) [1/2 definitions] |
| Apollyon |
according to the Book of Revelation, a destroying angel who is the king of the evil spirits that will torture those who do not bear the seal of God when the earth is destroyed; Abaddon. |
| Arctic Circle |
an imaginary line drawn around the earth parallel to the equator and south of the North Pole. |
| astronomer |
a scientist who studies the universe beyond the earth. |
| astronomical unit |
a unit of length based on the average distance of the earth from the sun, equal to about 149.6 million kilometers or ninety-three million miles. |
| astronomy |
the branch of science concerned with the physical universe beyond the atmosphere of the earth. |
| atmosphere |
the mass of gases surrounding the earth or any other celestial body. [1/3 definitions] |
| atmospheric |
of, pertaining to, or consisting of the mass of gases surrounding the earth. [1/2 definitions] |
| bank1 |
a heap or mass of something, such as earth or clouds. [3/6 definitions] |
| barium |
a chemical element of the alkaline-earth group that has fifty-seven protons in each nucleus and that is usu. found in compounds such as salts. (symbol: Ba) [1/2 definitions] |
| berm |
a low wall, mound, or barrier of earth, often one banked against the foundation of a building, to help insulate it. [1/3 definitions] |
| beryllium |
a chemical element of the alkaline-earth group that has four protons in each nucleus and occurs in pure form as a hard, light, gray solid, chiefly used in alloys with copper and in aerospace material. (symbol: Be) |
| biodiversity |
the diversity of life forms on earth or part of the earth, including diversity of species, genes, and ecosystems, esp. when regarded as providing the optimal conditions for evolution. |
| biosphere |
the part of the earth and its atmosphere in which living organisms can exist. |