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

The earlier attempt to set up an expert group within UN COPUOS to monitor satellite light pollution and impacts on astronomy was backed by Chile, Spain, Slovakia, Bulgaria, the Dominican Republic, Peru and South Africa. — Tereza Pultarova, Space.com, 28 Sep. 2026

Benioff had started in astronomy in 1917, working at both the Mount Wilson and Lick observatories. — Danny Robb, JSTOR Daily, 25 Sep. 2026

So, for example, Indian mathematics and Indian astronomy were very advanced. — David Brooks, The Atlantic, 20 Sep. 2026

After a decade spent in the Chinese city, the Finkelsteins moved again, this time to Haifa, Israel, where Peter studied painting and astronomy. — News Desk, Artforum, 17 Sep. 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