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

University of Regina astronomy professor, Samantha Lawler, has also questioned if SpaceX's constellations need to be so large and constantly refreshed when Starlink satellites can be retired in five years. —Michael Kan, PC Magazine, 14 Apr. 2026

This is part of the appeal — and the tension — of astronomy and astrotourism. —Jamie Carter, Space.com, 13 Apr. 2026

Following the return of the Artemis II astronauts’ and their circumnavigation around the moon, San Diegans can keep their eyes on the sky this week for a series of events focused on astronomy and the importance of dark skies. —Maura Fox, San Diego Union-Tribune, 13 Apr. 2026

Rangers offer regular astronomy programs from May through September. —Stephanie Vermillion, Travel + Leisure, 11 Apr. 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