planet

planet — noun

1. one of the huge bodies in space, roughly shaped like a ball, that circle a star

1.nounB1
Definition

one of the huge bodies in space, roughly shaped like a ball, that circle a star and shine with reflected light, such as Earth, Mars, or Jupiter.

Example

Earth is the only planet in our system known to support life.

planet + in our system

A new telescope found a rocky planet circling a star near Orion.

planet around + star

Common collocations
  • rocky planet
  • distant planet
  • other planets
  • planet orbiting a star
  • planet surface
Synonyms
  • world

    broader and common in science fiction, especially when a planet is treated as a place to live

  • exoplanet

    narrower scientific term for a planet outside our solar system

  • orb

    literary and uncommon; used more in descriptive writing than in science

Grammar Patterns

planet + around + star

life on + planet

the planet + name

Usage Note

Usually countable and often modified by words such as 'rocky', 'distant', or 'Earth-like'. Distinguish from sense 2 (THE WORLD): this sense names one object in space, not the shared home of human life.

Common Mistakes

Life may exist in other planets.
Life may exist on other planets.
English usually uses 'on' when a planet is treated as a place.
The Earth is the planet in our solar system.
The Earth is a planet in our solar system.
use 'a' when naming Earth as one member of a class.

2. the Earth thought of as the shared home of people, animals, and plants, especial

2.nounA2
Definition

the Earth thought of as the shared home of people, animals, and plants, especially when someone is talking about environmental harm or protection.

Example

Young volunteers spent Saturday cleaning the beach to help the planet.

environmental use: help the planet

Burning less fuel is one small way families can protect the planet.

protect the planet

Common collocations
  • save the planet
  • protect the planet
  • destroy the planet
  • across the planet
  • on the planet
Synonyms
  • Earth

    the most direct name for our planet

  • world

    common when the focus is people, society, or life across countries

  • globe

    often used in journalism or formal writing for the whole world

Grammar Patterns

save/protect the planet

on the planet

do something for the planet

Usage Note

Normally singular and usually used as 'the planet'. Common in environmental language such as 'save the planet', but it also appears in emphatic expressions like 'the only person on the planet' to mean 'in the whole world'.

Common Mistakes

We must protect planets.
We must protect the planet.
this sense usually means Earth as one shared world, so singular 'the planet' is normal.
Nobody in the planet knew the answer.
Nobody on the planet knew the answer.
the fixed expression uses 'on', not 'in'.
Idioms

to be on another planet | what planet is somebody on?

idiom

said, often humorously, when someone seems so far from real life that their ideas sound wildly impractical.

Dad says a weekend trip with four toddlers is relaxing; what planet is he on?

When the manager cut half the budget, Lina said he was on another planet.

Word family

Synonym discussion

Sense: noun/1

In everyday English, 'planet' is the basic scientific word for a large body that goes around a star. 'World' sometimes overlaps with it, but it more often presents the place as somewhere people, animals, or imaginary creatures might live, so it is especially common in fiction. 'Globe' is less astronomical; it usually means Earth itself or a round model of Earth, and in news writing it can mean the whole world. 'Exoplanet' is the precise science term for a planet outside our solar system. So astronomers discover an exoplanet, teachers explain the planets of our solar system, and a novel may describe a dangerous world at the edge of space.

planet ↗world ↗globe ↗exoplanet

Etymology

GreekLate LatinOld FrenchMiddle EnglishEnglish

English got 'planet' through Old French and late Latin from Greek 'planetes', a word meaning 'wanderer'. Ancient sky-watchers used it for the bright bodies that seemed to move across the sky instead of staying fixed like the stars.