Source : Webster's Revised Unabridged Dictionary (1913)

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.]

            Not from the stars do I my judgment pluck; And yet
            methinks I have astronomy.            --Shak.

   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.

   3. A treatise on, or text-book of, the science.

   {Physical astronomy}. See under {Physical}.

Source : WordNet®

astronomy
     n : the branch of physics that studies celestial bodies and the
         universe as a whole [syn: {uranology}]