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

Adam Frank is a professor of physics and astronomy at the University of Rochester and co-author ofThe Blind Spot. — Adam Frank, NPR, 14 Sep. 2026

Once there, Roman will study some of the biggest mysteries in astronomy, from dark energy to the formation of galaxies. — Thomas Fauchez, The Conversation, 14 Sep. 2026

China’s Five-hundred-meter Aperture Spherical radio Telescope (FAST) has achieved a significant breakthrough in astronomy. — Prabhat Ranjan Mishra, Interesting Engineering, 10 Sep. 2026

Though even before that happens, the research does point to the utility of gravitational wave astronomy to study some of the universe's most violent events. — Robert Lea, Space.com, 9 Sep. 2026

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