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

Those new to navigating the stars should also check out our guide to the top smartphone astronomy apps available in 2025. —Anthony Wood, Space.com, 15 Sep. 2025

Check my main feed for more in-depth articles on stargazing, astronomy, eclipses and more. —Jamie Carter, Forbes.com, 15 Sep. 2025

The study represents a significant milestone in gravitational wave astronomy, said Macarena Lagos, an assistant professor at the Institute of Astrophysics of the Universidad Andrés Bello in Chile. —Jacopo Prisco, CNN Money, 11 Sep. 2025

Detecting an electromagnetic counterpart to a black hole tearing apart a neutron star is among the holy grails of astronomy and astrophysics. —Chad Hanna, The Conversation, 10 Sep. 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