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

“If you use AI to advertise your restaurant, market, or anything else,” one person wrote, “I will know that you don’t care about food or the planet and I will never ever patronize your business.”

From Salon ● Oct. 3, 2026

Eight years ago, a Nasa Mars rover, Curiosity, explored a part of the planet named after Torridon.

From BBC ● Oct. 1, 2026

In “Digger,” directed by Alejandro González Iñárritu, Cruise is the one destroying the planet.

From The Wall Street Journal ● Oct. 1, 2026

Expect costumes, props and life-size vehicles from the film, as well as projection-based rooms designed to immerse guests in the desert planet of Arrakis.

From Los Angeles Times ● Sep. 30, 2026

“You want me to fix the planet just so humanity can take advantage of it again?”

From "Kwame Crashes the Underworld" by Craig Kofi Farmer

That material later became part of new generations of stars and planets and eventually contributed to the chemistry needed for life.

From Science Daily ● Oct. 2, 2026

Understanding when and how this material is lost matters because gas is essential for forming giant planets such as Jupiter and Saturn.

From Science Daily ● Sep. 28, 2026

Wrapped in thick jackets, woollen caps and gloves, tourists and visitors gather to see the Milky Way and look through telescopes at planets, the Moon and distant stars.

From BBC ● Sep. 26, 2026

They position telescopes for the night's planets and constellations before guiding visitors from local homestays.

From BBC ● Sep. 26, 2026

The planets glowed in the heavens; the moon and the sun each glowed with light.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife

Related Words

• asteroid
• earth
• globe
• sphere
• world