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.

Examples of astronomy in a Sentence

Recent Examples on the Web The Round Tower Climb the spiral ramp to the top of this city icon, built in 1642 as an observatory by King Christian IV, and enter the planetarium to learn about ancient and modern astronomy. Sunshine Flint, Travel + Leisure, 25 Nov. 2023 The mystery of why a universe full of matter gravitationally attracting all other matter hasn't yet collapsed on itself has haunted astronomy at least since Isaac Newton's introduction of a universal law of gravitation. Richard Panek, Scientific American, 14 Nov. 2023 Big telescopes on big launchers In 2021, the National Academies released a once-in-a-decade review of the top astronomy and astrophysics priorities for the US science community. Stephen Clark, Ars Technica, 18 Oct. 2023 Texts from that period emphasize the need for the doctor to be highly learned, including being well read in philosophy, logic, arithmetic and astronomy. Meg Leja, Smithsonian Magazine, 10 Nov. 2023 My father had a medical degree but always loved astronomy. Robin George Andrews, Quanta Magazine, 8 Nov. 2023 This rapid growth of the satellite industry has come at a cost for astronomers and fans of the night sky, as two new studies and panels at an international astronomy conference stressed this week. Ramin Skibba, WIRED, 6 Oct. 2023 Understanding how dark matter and dark energy work have been some of the most long-standing challenges in modern astronomy. Denise Chow, NBC News, 7 Nov. 2023 In fact, many of the physical sciences—such as astronomy and particle physics—rely on it as well, and can also suffer from replication difficulties. Condé Nast, The New Yorker, 30 Oct. 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 7 Dec. 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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