planetary

American  

[plan-i-ter-ee] / ˈplæn ɪˌtɛr i /

adjective

1. of, relating to, or resembling a planet or the planets.

2. wandering; erratic.

3. terrestrial; global.

4. Machinery. noting or pertaining to an epicyclic gear train in which a sun gear is linked to one or more planet gears also engaging with an encircling ring gear.

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noun

1. Machinery. a planetary gear train.

planetary British  

/ ˈplænɪtərɪ, -trɪ /

adjective

1. of or relating to a planet

2. mundane; terrestrial

3. wandering or erratic

4. astrology under the influence of one of the planets

5. (of a gear, esp an epicyclic gear) having an axis that rotates around that of another gear

6. (of an electron) having an orbit around the nucleus of an atom

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noun

1. a train of planetary gears

Other Word Forms

Derived Forms

• nonplanetary
  adjective

Etymology

Origin of planetary

From the Latin word planētārius, dating back to 1585–95. See planet, -ary

Explanation

The adjective planetary has to do with any astronomical body that revolves around a star — including the earth. Rather than a circle, planetary motion takes us in an elliptical shape around the sun. In science, planetary usually describes the attributes or motion of planets. It's also used for anything that behaves in a similar way, like planetary electrons, which revolve around their atomic nucleus as if they were tiny planets. You can also talk about things that affect our entire planet using this word: "She worries a lot about the planetary effects of climate change."

Example Sentences

He added: "The clock is ticking if we want to halt the worst effects of planetary warming but there is still time."

From BBC • Jun. 9, 2026

Roman, however, will search largely unexplored areas of the Milky Way, offering a much broader view of planetary systems across our galaxy.

From Science Daily • Jun. 1, 2026

As telescopes become more powerful, astronomers continue discovering increasingly unusual planetary systems across the galaxy.

From Science Daily • May 21, 2026

ESA Cheops project scientist Maximilian Günther says the discovery highlights how much scientists still do not understand about planetary origins.

From Science Daily • May 21, 2026

I look over at Brian’s house, wishing he were on his roof, wishing he knew how sorry I was, wishing he’d come over and talk about planetary orbits and solar flares.

From "I'll Give You the Sun" by Jandy Nelson

Related Words

• global
• terrestrial