astronomy

noun

as·​tron·​o·​my ə-ˈsträ-nə-mē 

plural astronomies

: the study of objects and matter outside the earth's atmosphere and of their physical and chemical properties

Did you know?

The Difference Between Astronomy and Astrology

Some may find it easy to confuse astronomy and astrology. At one time, these two words actually were synonymous (that is, astronomy once meant what astrology means today), but they have since moved apart from each other. In current use, astronomy is concerned with “the study of objects and matter outside the earth's atmosphere,” while astrology is the purported divination of how stars and planets influence our lives. Put bluntly, astronomy is a science, and astrology is not.

Examples of astronomy in a Sentence

Recent Examples on the Web

In the field of submillimeter astronomy, the scale of the collaboration is among the largest, Teague noted. —Asuka Koda, CNN Money, 5 Mar. 2026

Keeping binoculars steady for astronomy or wildlife spotting is one of the biggest barriers to accurate observations. —Matt Morris, Space.com, 4 Mar. 2026

For generations, eclipses have been surrounded by apocalyptic prophecies, which found a resurgence when there were four successive total lunar eclipses from 2014 to 2015, according to astronomy website EarthSky. —Hali Smith march 1, Idaho Statesman, 1 Mar. 2026

The answer, so common with astronomy, is maybe. —Phil Plait, Scientific American, 27 Feb. 2026

Word History

Etymology

Middle English astronomie "study of celestial bodies, including their possible influence on human affairs," borrowed from Anglo-French & Latin; Anglo-French astronomie, borrowed from Latin astronomia, borrowed from Greek astronomía "study of the stars, especially their movements," from astro- astro- + -nomia -nomy

First Known Use

12th century, in the meaning defined above

Phrases Containing astronomy

• radar astronomy
• radio astronomy
• X-ray astronomy

Rhymes for astronomy

• aeronomy
• agronomy
• autonomy
• economy
• gastronomy
• metonymy
• taxonomy
• deuteronomy

Kids Definition

astronomy

noun

as·​tron·​o·​my ə-ˈsträn-ə-mē 

plural astronomies

: the science of the heavenly bodies and of their sizes, motions, and composition

astronomer

-mər

noun