| astrolabe |
an instrument used by the ancient Greeks and medieval Arabs to determine the position of heavenly bodies, later replaced by the sextant. |
| astrology |
the study of the positions of the heavenly bodies in relation to each other with the aim of predicting their influence on human affairs. |
| astronaut |
a person trained to participate in space flight. |
| astronautics |
(used with a sing. verb) the science and technology of space travel. |
| astronomer |
a scientist who studies the universe beyond the earth. |
| astronomical |
of or pertaining to astronomy. [2 definitions] |
| 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. |
| astronomical year |
a unit of time equal to the period between one vernal equinox and the next. |
| astronomy |
the branch of science concerned with the physical universe beyond the atmosphere of the earth. |
| astrophotography |
the photographing of astronomical objects. |
| astrophysics |
(used with a sing. verb) the branch of physics that deals with the physical and chemical properties of heavenly bodies and interstellar space. |
| astute |
keen in understanding and judgment; shrewd. |
| Asunción |
the capital of Paraguay. |
| asunder |
in or into separate parts or pieces. [2 definitions] |
| as usual |
in the usual way; as always. |
| as well |
in addition; also; too. |
| as well as |
and also; and moreover. [2 definitions] |
| as yet |
up until now; up to this point. |
| asylum |
(old-fashioned) an institution for the care of those who are unable to maintain themselves, such as orphans or the severely mentally ill. [3 definitions] |
| asymmetric |
different, esp. in arrangement of space, on either side of a center line; not symmetrical; unbalanced. |
| asymmetry |
the state or quality of having two unidentical halves; lack of balance. |