The celestial orb which revolves round the earth; the
   satellite of the earth; a secondary planet, whose light, borrowed from
   the sun, is reflected to the earth, and serves to dispel the darkness
   of night. The diameter of the moon is 2,160 miles, its mean distance
   from the earth is 240,000 miles, and its mass is one eightieth that of
   the earth. See Lunar month, under Month.