as·​tron·​o·​my | \ ə-ˈsträ-nə-mē How to pronounce astronomy (audio) \
plural astronomies

Definition of astronomy

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

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 initial detection and subsequent tracing of FRB 121102 back to its origin point in a small dwarf galaxy more than 3 billion light-years away was a breakthrough in astronomy. Ashley Strickland, CNN, 8 June 2022 Join astronomer Dean Regas for these fast, fun and beginner classes on various topics in astronomy. Dean Regas, The Enquirer, 10 May 2022 In astronomy, matter comes in two flavors: dark matter and baryons. Joanna Thompson, Scientific American, 20 Apr. 2022 Webb will study the universe mainly in infrared, while Hubble observes mostly in visible and ultraviolet wavelengths, and in astronomy, the more wavelengths, the merrier. Marina Koren, The Atlantic, 25 Feb. 2022 Lisa Kaltenegger, an associate astronomy professor and the director of the Carl Sagan Institute at Cornell University, said the new discovery is further proof that planets can survive the demise of their stars. NBC News, 18 Oct. 2021 Isomers are also important in astronomy and astrophysics. Artemis Spyrou, The Conversation, 24 May 2022 Rowdy, 12, who shares a love of astronomy with brother, Christopher, 17, plans to study computer science. Joanne Fowler,, 3 Mar. 2022 Their best bet was to blend in with the male culture of astronomy. Ann Finkbeiner, Scientific American, 21 Mar. 2022 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'astronomy.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of astronomy

12th century, in the meaning defined above

History and Etymology for astronomy

Middle English astronomie, from Anglo-French, from Latin astronomia, from Greek, from astr- + -nomia -nomy

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The first known use of astronomy was in the 12th century

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Last Updated

20 Jun 2022

Cite this Entry

“Astronomy.” Dictionary, Merriam-Webster, Accessed 29 Jun. 2022.

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More Definitions for astronomy


as·​tron·​o·​my | \ ə-ˈsträ-nə-mē How to pronounce astronomy (audio) \

Kids Definition of astronomy

: a science that deals with objects and matter outside the earth's atmosphere and their properties

More from Merriam-Webster on astronomy

Nglish: Translation of astronomy for Spanish Speakers

Britannica English: Translation of astronomy for Arabic Speakers Encyclopedia article about astronomy


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