Definition of planet in English:

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Pronunciation: /ˈplanɪt/


1A celestial body moving in an elliptical orbit round a star.
Example sentences
  • Kepler showed that a planet moves round the Sun in an elliptical orbit which has the Sun in one of its two foci.
  • Nasa astronomers said they had found the smallest planets yet orbiting stars beyond our Sun.
  • The planets all orbit the Sun in the same direction, with orbital planes inclined slightly to the ecliptic.
1.1 (the planet) The earth: no generation has the right to pollute the planet
More example sentences
  • The high tax on petrol was put on in the first place to encourage people to use less of something which is polluting the planet.
  • Ten years ago at the Rio earth summit the world accepted the need to manage the planet as a single whole for the whole of the human race.
  • The idea behind the relay is to unite the world and infuse the planet with the Olympic spirit.
1.2chiefly Astrology & historical A celestial body distinguished from the fixed stars by having an apparent motion of its own (including the moon and sun), especially with reference to its supposed influence on people and events: the planets are presently influencing you in a positive way
More example sentences
  • It is difficult for the individual to see the extent to which the drive of the aspecting planet is influencing their life.
  • With the Sun as the ruler of the 2nd house, this trio of planets also influenced his economic affairs.
  • The effect is to harmoniously combine the influences of the planets.

The planets of the solar system are either gas giants—Jupiter, Saturn, Uranus, and Neptune—or smaller rocky bodies—Mercury, Venus, Earth, and Mars. Pluto, formerly regarded as the ninth planet, was in 2006 reclassified as a dwarf planet. The minor planets, or asteroids, orbit mainly between the orbits of Mars and Jupiter. Only Earth and Venus have substantial atmospheres.


what planet are you on?

British informal Used to indicate that someone is out of touch with reality.
Example sentences
  • What planet are you on mate if you think this only happens in the Australian Football League?
  • And as for stealing the election from her, what planet are you on?



Example sentences
  • So in some respects, by studying Titan's atmosphere, planetologists are probing the early history of the Earth, particularly its early atmospheric chemistry.
  • Evolutionary biologists, planetologists, archaeologists and all those academics who dig up the past confirm evidence of different life forms at given periods.
  • Not to mention twelve planetologists, five zoologists, somewhere around thirty industrial miners.


Pronunciation: /planɪˈtɒlədʒi/
Example sentences
  • If, however, the human race has now reached the technical capability to carry on some of its industrial activities in space, we should indulge in the mental exercise of ‘comparative planetology.’
  • He criticized the commission for coming up with a set of goals for the exploration program that included topics such as studies of the Big Bang and comparative planetology but omitted a clear statement about searching for life on Mars.
  • Many characteristics of the Earth are quite unique, and recent discoveries under-scoring this are causing a turn toward viewing planetology as a study of contrasts with Earth, not similarities to it.


Middle English: from Old French planete, from late Latin planeta, planetes, from Greek planētēs 'wanderer, planet', from planan 'wander'.

  • Early Greek astronomers observed certain heavenly bodies moving around the night sky in contrast to the stars, which stayed permanently in a fixed position in relation to one another. This is why they are called planets, from Greek planētēs ‘wanderer’. The Sun and the Moon were once thought of as planets too. Plankton, the term for small and microscopic organisms floating in the sea, comes via German from the related Greek word planktos, ‘wandering or drifting’. See also aeroplane

Words that rhyme with planet

gannet, granite, Janet

For editors and proofreaders

Line breaks: planet

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