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

Algebra exists because Greek geometry, Persian astronomy, and Indian arithmetic landed for the first time in one language and one ninth-century mind — al-Khwārizmī’s. —Christian Catalini, Forbes.com, 11 June 2026

Examples include words like alcohol, alkali, alchemy, and in astronomy, star names such as Altair, Alkaid, Alcor and Aldebaran. —Scott Neuman, NPR, 11 June 2026

To better understand how society might react requires the input of academics and experts from many disciplines beyond astronomy. —Keith Cooper, Space.com, 9 June 2026

Learning from Crystal Ball Nebula observations Jan Cami, a professor of physics and astronomy at Western University in London, Ontario, compares planetary nebulae to butterflies because of their diverse colors and shapes. —Avni Trivedi, CNN Money, 8 June 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