plan·​et ˈpla-nət How to pronounce planet (audio)
: any of the large bodies that revolve around the sun in the solar system
: a similar body associated with another star
: earth
usually used with the
one of the hottest places on the planet
: any of the seven celestial bodies sun, moon, Venus, Jupiter, Mars, Mercury, and Saturn that in ancient belief have motions of their own among the fixed stars
: a celestial body held to influence the fate of human beings
: a person or thing of great importance : luminary
planetlike adjective
planet table

Did you know?

Planet goes back to ancient Greek planēt- (literally, "wanderer"), which is derived from planasthai, a Greek verb which means "to wander." The word was originally applied to any of seven visible celestial bodies which appeared to move independently of the fixed stars—the sun, the moon, Mercury, Venus, Mars, Jupiter, and Saturn. In line with astronomical discovery and advancement, planet began to be used specifically of the rocky or gaseous bodies that orbit around the sun—a definition which excluded the moon and the sun but included the Earth and, as they were discovered, Uranus, Neptune, and Pluto. In 2006, the International Astronomical Union developed a narrower definition of planet, effectively demoting Pluto to the status of a "dwarf planet," a celestial body that is spherical and orbits the sun but is not large enough to disturb other objects from its orbit.

Examples of planet in a Sentence

our collective responsibility to conserve the planet and its natural resources for future generations
Recent Examples on the Web And the mission, as Ms. McKenzie describes it, was to develop an alternative fuel source that could power cars and trucks without releasing the greenhouse gases largely responsible for the planet’s rapid heating, and that have been particularly devastating to small island states like this one. Stephanie Hanes, The Christian Science Monitor, 21 Nov. 2023 There, whatever goes up must come down, pulled back to our planet by a steady wash of speed-sapping atmospheric particles. Meghan Bartels, Scientific American, 21 Nov. 2023 Sign up for the Climate Coach newsletter and get advice for life on our changing planet, in your inbox every Tuesday and Thursday. Chico Harlan, Washington Post, 21 Nov. 2023 The thrill is in the hunt for the most exceptional stones on the planet and discovering exciting new talents designing pieces coveted for their contemporary beauty and distinctive style. Jill Newman, Robb Report, 18 Nov. 2023 The two men spent four hours exploring the planet’s deepest spot. William J. Broad, New York Times, 18 Nov. 2023 Scientists from Italy have recently published a study that shows how our planet’s ionosphere was impacted as a result of its high intensity and long duration. Dhananjay Khadilkar, Ars Technica, 17 Nov. 2023 Shiner: And the ones that struck our planet brought water. Chris Klimek, Smithsonian Magazine, 16 Nov. 2023 There are lots of other things afoot on both planets. Alan Sepinwall, Rolling Stone, 10 Nov. 2023 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'planet.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


Middle English planete, from Anglo-French, from Late Latin planeta, modification of Greek planēt-, planēs, literally, wanderer, from planasthai to wander — more at floor

First Known Use

14th century, in the meaning defined at sense 1a

Time Traveler
The first known use of planet was in the 14th century


Dictionary Entries Near planet

Cite this Entry

“Planet.” Dictionary, Merriam-Webster, Accessed 29 Nov. 2023.

Kids Definition


plan·​et ˈplan-ət How to pronounce planet (audio)
: a heavenly body other than a comet, asteroid, or satellite that travels in orbit around the sun
also : such a body orbiting another star
planet table

Middle English planete "planet," from early French planet (same meaning), from Latin planeta (same meaning), from Greek planēt-, planēs "planet," literally, "wanderer"

Word Origin
Most of the stars seem to have fixed positions when they are compared to other stars. There are some heavenly bodies, however, that clearly change their positions in relation to the stars and to each other. They seem to wander about among the fixed stars. The ancient Greek name for such a heavenly body was planēs, which means "wanderer." The English word planet comes from the Greek planēs. Unlike the ancient Greeks, we now know that the planets "wander" across the sky because they are revolving around the sun.

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