plan·​et | \ˈpla-nət \

Definition of planet 

1a : 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

b(1) : any of the large bodies that revolve around the sun in the solar system

(2) : a similar body associated with another star

c : earth usually used with the

2 : a celestial body held to influence the fate of human beings

3 : a person or thing of great importance : luminary

planet table

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Other Words from planet

planetlike \ˈpla-​nət-​ˌlīk \ adjective

Synonyms for planet


earth, globe, world

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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 name "planet" 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 the 17th century, "planet" began to be used specifically of the rocky or gaseous bodies that orbit around the sun - a definition which excluded the moon and, obviously, 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

Another experiment will calculate Mars’ wobble to reveal the makeup of the planet’s core. Marcia Dunn, The Seattle Times, "Mars touchdown: NASA spacecraft survives supersonic plunge," 28 Nov. 2018 Within moments after touching down, InSight took a picture of the red planet's surface, with its hazy atmosphere in the background. Eric Berger, Ars Technica, "NASA does it again by landing safely on Mars—something no one else has done," 26 Nov. 2018 If all goes to plan, scientists hope that by studying the deep interior of Mars InSight will open a window into the processes that shaped the rocky planets of the inner solar system, including Earth, more than four billion years ago. Robert Lee Hotz, WSJ, "NASA’s InSight Spacecraft Lands Safely on Mars," 26 Nov. 2018 What’s more, our frivolous impulse buys are absolutely horrible for the planet. Rebekka Ayres, Teen Vogue, "Black Friday, Explained: A Complete History," 23 Nov. 2018 The CONNection EXplorer—or CONNEX for short—consists mainly of a satellite that will fire electron particles at the planet. Avery Thompson, Popular Mechanics, "A Group of Scientists Want to Launch a Satellite to Make an Artificial Aurora," 29 Oct. 2018 But only a few hours later, Mercury (the planet of communication) begins its twirl backward. Aliza Kelly Faragher, Allure, "What November's Cancer Horoscope Means for You," 28 Oct. 2018 Additionally, Venus’s atmosphere is mainly carbon dioxide and thick clouds of sulfuric acid cover the entire planet. Fox News, "NASA eyes stunning 'cloud city' airship concept to explore Venus," 16 Oct. 2018 Many of the key issues facing our society—and planet as a whole—are rooted in science and technology, so scientists should play a role in solving them at a government level, Naughton argues. Hans Aschim, Harper's BAZAAR, "Could More Female Scientists in Public Office Save America?," 8 Oct. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'planet.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of planet

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

History and Etymology for planet

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

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2 Dec 2018

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Time Traveler for planet

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

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More Definitions for planet


plan·​et | \ˈpla-nət \

Kids Definition of planet

: any large heavenly body that orbits a star (as the sun)

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More from Merriam-Webster on planet

Rhyming Dictionary: Words that rhyme with planet

Thesaurus: All synonyms and antonyms for planet

Spanish Central: Translation of planet

Nglish: Translation of planet for Spanish Speakers

Britannica English: Translation of planet for Arabic Speakers Encyclopedia article about planet

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a nest or breeding place

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