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

Simulating a lifeless Earth The simulation builds on an earlier model developed in the laboratory of Rory Barnes, an associate professor of astronomy at the University of Washington. — Neetika Walter, Interesting Engineering, 3 Nov. 2026

Swift’s contributions to astronomy, particularly the study of gamma-ray bursts (GRBs), cannot be overstated. — Andrew Paul, Popular Science, 2 Nov. 2026

If the neutrino’s source of origin is hidden at gamma-ray wavelengths, but not at radio wavelengths, then radio telescopes could become an essential tool in neutrino astronomy. — Yjan Gordon, The Conversation, 30 Oct. 2026

My brain is a rat’s nest of judicial decisions, fun facts about small mammals, and lots and lots of astronomy stuff. — Sam MacDonald, Scientific American, 28 Oct. 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