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 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 The institute conducts research in a variety of fields related to astrobiology, astronomy, and space science, with a primary focus on detecting signals or signs of intelligent life in the universe. Katie Liu, Discover Magazine, 25 Oct. 2023 Physics, chemistry, astronomy, geology, biology, and ecology all affirm that existence is relational at all scales of space, life, and time. Carl Safina, TIME, 5 Oct. 2023 Home to seven mysterious planets—each around the size of our own Earth—the TRAPPIST-1 system is regarded by some as the crown jewel of astronomy’s efforts to find life in the Milky Way. Kaitlin Rasmussen, Scientific American, 14 Sep. 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 28 Nov. 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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