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

This will arguably mark the biggest moment in astronomy since the first images from the James Webb Space Telescope (JWST) were revealed in the summer of 2022. —Robert Lea, Space.com, 20 June 2025

The Magnum photographer’s new book, Blinked Myself Awake, combines memoir and image in a series of eclectic riffs on the history of astronomy, the practice of stargazing—both amateur and professional—and the relationship between photography and objectivity. —Tyler Austin Harper, The Atlantic, 7 June 2025

While astronomy and clouds don’t usually mix, a rare type of atmospheric phenomenon, called noctilucent or night-shining clouds, offers an exception, as reported by Space.com’s Anthony Wood. —Margherita Bassi, Smithsonian Magazine, 30 May 2025

Favorite viewing spots like East Rim Overlook and Bandy Creek offer wide-open skies, and the park regularly teams up with groups like the Knoxville Observers and Eastern Kentucky University to host stargazing events and astronomy nights. —Lydia Mansel, Southern Living, 8 June 2025

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