planet

American  

[plan-it] / ˈplæn ɪt /

noun

• planets
  plural

1. Astronomy.

   1. Also called major planet.  any of the eight large heavenly bodies revolving about the sun and shining by reflected light: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, or Neptune, in the order of their proximity to the sun. Until 2006, Pluto was classified as a planet ninth in order from the sun; it has been reclassified as a dwarf planet.

   2. a similar body revolving about a star other than the sun.

   3. (formerly) a celestial body moving in the sky, as distinguished from a fixed star, applied also to the sun and moon.

2. Astrology. the sun, moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, or Pluto: considered sources of energy or consciousness in the interpretation of horoscopes.

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planet British  

/ ˈplænɪt /

noun

1. Also called: major planet.  any of the eight celestial bodies, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune, that revolve around the sun in elliptical orbits and are illuminated by light from the sun

2. Also called: extrasolar planet.  any other celestial body revolving around a star, illuminated by light from that star

3. astrology any of the planets of the solar system, excluding the earth but including the sun and moon, each thought to rule one or sometimes two signs of the zodiac See also house

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planet Scientific  

/ plăn′ĭt /

1. In the traditional model of solar systems, a celestial body larger than an asteroid or comet, illuminated by light from a star, such as the Sun, around which it revolves.

2. A celestial body that orbits the Sun, has sufficient mass to assume nearly a round shape, clears out dust and debris from the neighborhood around its orbit, and is not a satellite of another planet. The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto was considered to be a planet until its reclassification in 2006 as a dwarf planet. A planetlike body with more than about ten times the mass of Jupiter would be considered a brown dwarf rather than a planet.

3. See also extrasolar planet inner planet outer planet

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planet Cultural  

1. An object in orbit around a star. A planet does not give off its own light; rather, it shines by reflecting sunlight. Planets close to the sun are rocky. Those farther out consist mostly of gas es and liquids.

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Discover More

There are nine major planets, including the Earth, in orbit around our sun, along with many asteroids. (See solar system.)

Scientists have discovered evidence for the existence of many planets that circle other stars.

Other Word Forms

Noun Inflected Forms

• planets
  plural

Etymology

Origin of planet

1250–1300; Middle English planete (< Old French planète ) < Late Latin planēta, planētēs (found only in plural planētae ) < Greek ( astéres ) planḗtai literally, wandering (stars)

Explanation

A planet is a celestial body that revolves around a star. In our solar system, Earth is the third planet from the sun. The word planet comes from the Greek planetes, which means "wanderer." Since ancient times, people have been fascinated by the wandering of celestial bodies in the night sky. If a variety of factors come together so that something works out well for you, you can say that the planets aligned. You parents weren't sure if your family was going to be able to go on vacation, but then the planets aligned and off to Florida you were.

Example Sentences

See Examples For:

planet planets

So-called public benefit corporations do actually exist, and with a triple bottom line: a dedication to people, planet and profit, essentially in that order.

From Salon ● Aug. 19, 2026

That’s when the biggest club on the planet came calling again.

From The Wall Street Journal ● Aug. 18, 2026

Cristiano Ronaldo grew up in poverty on the remote island of Madeira, but became football's first billionaire player, and one of the most recognisable people on the planet.

From BBC ● Aug. 16, 2026

You have to ask, “what are we doing to the planet and does that mean we will encounter more diseases?” said Janet Foley, a disease ecologist at the UC Davis School of Veterinary Medicine.

From Los Angeles Times ● Aug. 16, 2026

By morning, I’d decided that the chance to travel to another planet—a planet of cats!—was too awesome to miss.

From "Klawde: Evil Alien Warlord Cat" by Johnny Marciano and Emily Chenoweth

Anderson says much of his work involving clay deposits was originally motivated by the search for life on other planets.

From Science Daily ● Aug. 17, 2026

When Lantern Corps members unite their rings’ powers, they can move planets.

From Salon ● Aug. 16, 2026

Alex Grant, a chemical engineer from Toronto, started a magnesium-smelting company in 2022 and named it Magrathea after a planet in Douglas Adams’s “The Hitchhiker’s Guide to the Galaxy” whose inhabitants build other planets.

From The Wall Street Journal ● Aug. 14, 2026

Stars and planets appear in the sky next to the blotted-out Sun.

From Barron's ● Aug. 5, 2026

Swift had read Cyrano, and Gulliver is a cunning variation on the by then conventional themes of science fiction, one in which islands are substituted for planets.

From "The Invention of Science" by David Wootton

Related Words

• asteroid
• earth
• globe
• sphere
• world