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

The damage threatens one of the Bay Area’s most significant scientific landmarks — a telescope that helped shape modern astronomy and still draws thousands of visitors each year to the mountaintop east of San Jose. —Ethan Baron, Mercury News, 31 Dec. 2025

Located atop Palomar Mountain in North County, the Palomar Observatory is home to the 200-inch Hale Telescope, one of the most important telescopes in the history of astronomy. —Abby Hamblin, San Diego Union-Tribune, 30 Dec. 2025

If the weather permits, astronomy enthusiasts will be able to see stars, planets, the Milky Way, and, potentially, meteor showers from Mayo Dark Sky Park, an International Dark Sky reserve in County Mayo. —Lydia Mansel, Travel + Leisure, 29 Dec. 2025

The Roman Space Telescope is one of NASA's next great observatories, designed to explore some of the biggest questions in modern astronomy. —Kenna Hughes-Castleberry, Space.com, 25 Dec. 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