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

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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)

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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

The mystery surrounding 70 Oph AB began long before modern planet hunting.

From Science Daily ● Oct. 30, 2026

Researchers found that the planet has warmed at a rate of approximately 0.35°C per decade over the past 10 years, although the exact figure varies depending on the temperature dataset used.

From Science Daily ● Oct. 30, 2026

The researchers concluded that variations in stellar surface activity over time, rather than the gravitational influence of a giant planet, were responsible for the mysterious wobble.

From Science Daily ● Oct. 30, 2026

"When did ice start forming on the planet and what did those natural processes of loss look like?" said Thompson.

From Science Daily ● Oct. 29, 2026

The planet would cool, likely for several years.

From "Fallout: Spies, Superbombs, and the Ultimate Cold War Showdown" by Steve Sheinkin

If they had existed in perfectly equal quantities, virtually all matter could have disappeared, leaving no material to form stars, planets, or life.

From Science Daily ● Nov. 1, 2026

Around 70 Oph A, no such planets were found within 5 astronomical units.

From Science Daily ● Oct. 30, 2026

Although William Jacob's original claim from 1855 did not withstand later examination, measurements collected over the following 171 years had never completely eliminated the possibility of giant planets in the system's inner regions.

From Science Daily ● Oct. 30, 2026

By eliminating certain possibilities, the researchers have provided information that could make future searches more efficient and help astronomers focus on planets that remain within reach of upcoming observatories.

From Science Daily ● Oct. 30, 2026

This philosophy—the interchangeability of music, math, and nature—led to the earliest Pythagorean model of the planets.

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

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