as·​tron·​o·​my ə-ˈsträ-nə-mē How to pronounce astronomy (audio)
plural astronomies
: the study of objects and matter outside the earth's atmosphere and of their physical and chemical properties

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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.

Example Sentences

Recent Examples on the Web In astronomy, researchers use optical frequency combs to measure the frequencies of light coming from distant stars; disruptions can indicate a star has an exoplanet. Starre Vartan, Scientific American, 12 May 2023 There’s a range of events to keep newfound friends busy, including outdoor music performances, stargazing tours, photography lessons and astronomy education programs for kids. Lilit Marcus, CNN, 19 Apr. 2023 The treatise on the meteoroscope is a description of how to use the instrument for observations, as well as for doing astronomy calculations. Dhananjay Khadilkar, Ars Technica, 18 Apr. 2023 The first is basic astronomy: Simply put, Stonehenge’s neolithic architects would have no way of precisely accounting for the subtle change in the sun’s daily position (which accounts to one-tenth of a degree) using massive stones. Darren Orf, Popular Mechanics, 28 Mar. 2023 To easily view the planetary alignment, Star Walk recommends using the astronomy app Sky Tonight. Ariana Garcia, Chron, 22 Mar. 2023 When Pía Urbano Mena, the astronomy guide at the Nayara Alto Atacama, turned off the ambient lights at the hotel's small observatory, there was a magic, neck-tingling moment as the inky blackness absolutely enveloped us. Tom Vanderbilt, Condé Nast Traveler, 15 Mar. 2023 Similar to last year, there are educational toys and STEM sets that give kids hand-on experience with topics that fascinate kids, from astronomy to magic. Jessica Hartshorn,, 9 May 2023 Over on Reddit‘s r/astronomy, for example, a user who later deleted their account — perhaps in embarrassment — asked if the celestial body was once yellow. Miles Klee, Rolling Stone, 4 May 2023 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'astronomy.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


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

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

Dictionary Entries Near astronomy

Cite this Entry

“Astronomy.” Dictionary, Merriam-Webster, Accessed 8 Jun. 2023.

Kids Definition


as·​tron·​o·​my ə-ˈsträn-ə-mē How to pronounce astronomy (audio)
plural astronomies
: the science of the heavenly bodies and of their sizes, motions, and composition

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