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

Cassini carried 12 science instruments to study Saturn, often observing the planet and its moons in ways invisible to the human eye. Joe Pappalardo, Popular Mechanics, "Saturn and Its Moon Enceladus Talk To Each Other. The Sound Is Perfectly Cosmic and Eerie.," 10 July 2018 James Webb, the successor to the Hubble Space Telescope, is meant to revolutionize the world's understanding of planet and star formation. Alex Stuckey, Houston Chronicle, "NASA's James Webb telescope will study Jupiter's Red Spot -- if it ever launches," 5 July 2018 Visitors can observe the stars, planets and other celestial objects through telescopes. Brendel Hightower, Detroit Free Press, "Things to do in metro Detroit for the week of July 1 and beyond," 1 July 2018 Get ready to race between planets and deep space, starting with the goings-on on Jupiter. Shannon Stirone, WIRED, "Space Photos of the Week: Scientists Are Seeing Red Over Jupiter’s Spot," 30 June 2018 Mercury is the planet of communication, and within astrology, its task is to ensure that messages are successfully delivered through verbal dialogue, written correspondence, technology, and transportation. Aliza Kelly Faragher, Allure, "What Your Sign's July 2018 Horoscope Predictions Mean for You," 29 June 2018 The findings are expected to shed light on the materials that existed in the early solar system and the formation and evolution of planets and their arrangement. Dennis Normile, Science | AAAS, "Japan’s new asteroid probe reaches its target after 3.2-billion-kilometer journey," 27 June 2018 Above us are an untold number of stars and planets and other geologic wonders, and likely, life. Brian Resnick, Vox, "Summer is for meteor showers and stargazing. Here’s how to watch.," 22 June 2018 Old friends Wearing a bandanna at his neck, blue jeans, a Western shirt and cosmic jacket decorated with planets and a Space Shuttle, Fogerty treated his audience to 13 Creedence Clearwater Revival songs. David Lindquist, Indianapolis Star, "5 ways John Fogerty keeps it timeless in Indianapolis," 14 June 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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Phrases Related to planet

preserve the planet

Statistics for planet

Last Updated

9 Sep 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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Comments on planet

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to make amends

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