Astronomy (noun)

1. The study of objects and matter outside the Earth's atmosphere and of their physical and chemical properties.
2. The study of the universe and its contents, including the sun, moon, stars, planets, and other celestial bodies and phenomena.

Origin:

Late middle english: from old french astronomie, from latin astronomia, from greek astronomia, from astro- "star" + -nomos "arranger" (from nemein "to distribut.e")

Examples:

1. Astronomy is one of the oldest sciences.
2. The telescope has been a key tool in the study of astronomy.
3. The astronomy department at the university has a new observatory.
4. The study of astronomy has led to many discoveries about our universe.
5. The amateur astronomer spent his nights observing the night sky.