From WordNet (r) 3.0 (2006) [wn]:
astronomy
n 1: the branch of physics that studies celestial bodies and the
universe as a whole [syn: astronomy, uranology]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Astronomy \As*tron"o*my\, n. [OE. astronomie, F. astronomie, L.
astronomia, fr. Gr. ?, fr. ? astronomer; 'asth`r star + ? to
distribute, regulate. See Star, and Nomad.]
1. Astrology. [Obs.]
[1913 Webster]
Not from the stars do I my judgment pluck;
And yet methinks I have astronomy. --Shak.
[1913 Webster]
2. The science which treats of the celestial bodies, of their
magnitudes, motions, distances, periods of revolution,
eclipses, constitution, physical condition, and of the
causes of their various phenomena.
[1913 Webster]
3. A treatise on, or text-book of, the science.
[1913 Webster]
Physical astronomy. See under Physical.
[1913 Webster]