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

For Webster, it's about "allowing our mother – the planet Earth – a voice again".

From BBC ● Aug. 1, 2026

A strengthening El Nino that could shatter all-time records is "adding fuel to a planet already on fire" and pushing the world into "uncharted territory," UN Secretary-General Antonio Guterres warned Friday.

From Barron's ● Jul. 31, 2026

Soccer’s velvety, polarizing honcho had the planet begrudgingly tossing confetti at his custom Stan Smiths.

From The Wall Street Journal ● Jul. 31, 2026

Both “Secret Wars” series saw characters displaced onto a patchwork planet called Battleworld.

From Los Angeles Times ● Jul. 31, 2026

“I get it. A hundred years ago is a different planet from today, and here you are, unable to enjoy any of the advancements society has made. Tough.”

From "The Manifestor Prophecy" by Angie Thomas

Together, they can focus on objects across deep space and help researchers work out how planets and stars form and galaxies evolve, and study other space phenomena.

From BBC ● Jul. 29, 2026

A radio telescope like the giant Lovell dish catches radio signals from distant stars, galaxies and planets in space, turning them into pictures and scientific data.

From BBC ● Jul. 28, 2026

The researchers now plan to apply their theory to additional moons and to possible exomoon systems around distant planets.

From Science Daily ● Jul. 27, 2026

They are later incorporated into new stars, planets, and other cosmic material.

From Science Daily ● Jul. 25, 2026

He takes for granted a central issue that was resolved only by the discovery of the phases: that planets shine by reflected light.

From "The Invention of Science" by David Wootton

Related Words

• asteroid
• earth
• globe
• sphere
• world