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

Eric Berger is the senior space editor at Ars Technica, covering everything from astronomy to private space to NASA policy, and author of two books: Liftoff, about the rise of SpaceX; and Reentry, on the development of the Falcon 9 rocket and Dragon. —Eric Berger, ArsTechnica, 14 May 2025

This fall, Phoenix will welcome a first-of-its-kind International Dark Sky Discovery Center, a 23,000-square-foot astronomy hub with an observatory, planetarium, and immersive exhibits. —Stephanie Vermillion, Travel + Leisure, 8 May 2025

Courtesy of Atlas Ocean Voyages Imagine travel that effortlessly connects you more deeply with local experts in music, history, gastronomy, and astronomy. —Atlas Ocean Voyages, AFAR Media, 7 May 2025

For between 30 to 40 minutes before sunrise on Friday, April 25, the slender waning crescent moon appeared to left of a bright planet Venus and a much fainter Saturn to create a happy face, according to astronomy news outlet EarthSky. —James Powel, USA Today, 30 Apr. 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