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

Starship is set to fly at an altitude of about 275 kilometers above Earth and complete six orbits around the planet.

From MarketWatch ● Sep. 15, 2026

Here is a look at the battle lines in the war over a technology that is now the backbone of the economy and could decide the future of the planet.

From Barron's ● Sep. 15, 2026

It’s a great day for people who hate the idea of a livable planet.

From Slate ● Sep. 14, 2026

Ellison is one of the richest people on the planet, but he might also be one of the world’s most indebted and much of his wealth is tied to his Oracle stake.

From The Wall Street Journal ● Sep. 12, 2026

In that drop of water, Leeuwenhoek found a whole new planet of very, very small life forms.

From "Phineas Gage" by John Fleischman

Jupiter and Venus are two of the planets which will be easy to see in the sky in mid-November.

From BBC ● Sep. 12, 2026

All four planets will be above the horizon before sunrise, although some will be easier to spot than others.

From BBC ● Sep. 12, 2026

SpaceX wants the vehicle to carry artificial-intelligence and next-generation Starlink satellites to low-Earth orbit, as well as ferry people and cargo to other planets.

From MarketWatch ● Sep. 8, 2026

“When I was young, I really just wanted to work in a starship or a spaceship and look at other planets and explore other planets,” she said.

From Los Angeles Times ● Sep. 8, 2026

This work would not come to fruition until Johannes Kepler drew upon Tycho’s tables to explain the orbits of the planets, years after Tycho had died.

From "The Scientists" by John Gribbin

Related Words

• asteroid
• earth
• globe
• sphere
• world