DictionaryAI

planet

noun
PLAN-it/ˈplænɪt/

Pluralplanets

3 meanings of planet

Practice

  1. 1
    nouncountable
    A large, nearly round natural body that orbits a star, is not itself a star, and dominates the region around its orbit; in older usage, also smaller bodies orbiting the Sun, such as asteroids.

    Each planet in our solar system follows its own path around the Sun.

    The newly discovered planet orbits a star forty light-years away.

    UsageUse on for where life exists: life on a planet, life on Mars.

    Similarworld

    Note

    The IAU's version adds the sorting test: a planet must dominate the region of its orbit. A body that orbits the Sun and is rounded by its own gravity, but is not a moon and lacks that dominance, is a dwarf planet. That is how Pluto left the list. Alok Jha in The Guardian (2006) reports eight planets and three dwarf planets. Nothing ties the sense to the Sun, so the planets of other stars count, and world can stand in for it.

  2. 2
    Earthnouncountable
    The Earth, regarded as the world inhabited by humankind.

    Human activity is putting enormous strain on the planet's resources.

    This planet is the only home our species has ever known.

    UsageCommon expressions meaning Earth include the planet, this planet, and our planet: save the planet, protect our planet.

    Similarworld, globe

    Note

    The article carries the meaning here: with the or this in front, planet needs no name to mean Earth. The planet suits talk of the world as a whole, as in "the oneness or fragility of the planet." This planet adds a speaker's wry distance. In Robert W. Chambers's The Younger Set (1907), a character prefers "the garishly sunlit side of this planet."

    Checked 2 Nov 2026 · 3 facts

    • The quoted example occurs verbatim. theguardian.com
    • Robert W. Chambers wrote The Younger Set, first published in 1907. gutenberg.org
    • The quotation is accurate and expresses the character Selwyn's preference. gutenberg.org
  3. 3
    wandering starnounhistoricalcountable
    In ancient and medieval astronomy, and still in astrology, one of the seven bodies that move against the fixed stars: the Sun, the Moon, Mercury, Venus, Mars, Jupiter, and Saturn.

    Medieval scholars assigned each planet its own crystalline sphere.

    Another of Boehme's followers, the Welshman Morgan Llwyd, also believed that the seven planets could be found within man.
    1971, Keith Thomas, Religion and the Decline of Magic
    Note

    The sense the name was made for. Greek planḗtēs meant "wanderer," short for "wandering stars": the lights that moved while the fixed stars kept their places. By that reckoning the Sun and Moon were planets too, and Henry Fielding's Tom Jones (1749) still calls the moon "that beautiful planet." The seven now survive mainly in astrology, so this is the sense to use for older cosmology or horoscopes.

    Checked 1 Nov 2026 · 6 facts

    • The original astronomical sense concerned the wandering celestial lights. en.wikipedia.org
    • Greek planḗtēs meant wanderer; its astronomical use shortened an expression meaning wandering star. en.wiktionary.org
    • Planets appeared to move against stars whose relative positions appeared fixed. en.wikipedia.org
    • The classical seven planets included the Sun and Moon. en.wikipedia.org
    • Henry Fielding wrote Tom Jones, first published in 1749. en.wikisource.org
    • The novel's narrator refers to the Moon as 'that beautiful planet'. gutenberg.org

Practice

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Origin

The word came into Middle English from Old French planete, from Latin planeta, from Ancient Greek planḗtēs ("wanderer"): a shortening of astéres planêtai ("wandering stars"), from planáō ("to wander about, stray"), which is of unknown origin. They were so named because they appear to move, unlike the "fixed" stars, and the modern scientific sense of a "world that orbits a star" dates from the 1630s in English.

Checked 1 Nov 2026 · 6 facts

  • Middle English borrowed the word from Old French planete, ultimately through Latin planeta from Ancient Greek planḗtēs, meaning wanderer. en.wiktionary.org
  • The astronomical Greek expression was shortened from astéres planêtai, meaning wandering stars. en.wiktionary.org
  • Planḗtēs derives from planáō, meaning to wander or stray. en.wiktionary.org
  • The further origin of planáō is unknown. en.wiktionary.org
  • The name reflects apparent movement against the fixed stars. en.wikipedia.org
  • The English scientific sense of a world orbiting a star dates from the 1630s. en.wiktionary.org