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

Scientists led by UC San Diego's Scripps Institution of Oceanography are warning that oxygen is disappearing rapidly from oceans and freshwater systems, potentially pushing the planet into an "unsafe space."

From Science Daily ● Jul. 20, 2026

Its president, Alejandro Dominguez, said it would ensure "nobody on the planet is left out of the party".

From BBC ● Jul. 20, 2026

Otherwise you’re just railing in impotent fury at the companies frying the planet.

From MarketWatch ● Jul. 17, 2026

But no matter what happens in the World Cup final, the biggest sporting event on the planet has already produced a winner—and it’s neither European nor Messi.

From The Wall Street Journal ● Jul. 17, 2026

Natalie and Shannon might have been from very different parts of the city, but they were from the same planet after all.

From "Two Degrees" by Alan Gratz

As a result, the resonance acts like an escape route from the main asteroid belt, pushing objects into elongated orbits that cross the paths of planets.

From Science Daily ● Jul. 18, 2026

Many stars are poor candidates because chemical signatures from swallowed planets can fade or become difficult to distinguish.

From Science Daily ● Jul. 16, 2026

Astronomers have found strong evidence that TOI-5882, a sun-like star about 1,300 light-years from Earth, may have consumed one of its own planets.

From Science Daily ● Jul. 16, 2026

According to Noto, worlds with permanent day and night are actually much more common than planets like Earth, which experience a regular day and night cycle.

From Science Daily ● Jul. 9, 2026

How did Donne know that the new philosophers were seeking new worlds, not only by thinking of the planets as worlds but also by looking for worlds elsewhere in the firmament?

From "The Invention of Science" by David Wootton

Related Words

• asteroid
• earth
• globe
• sphere
• world