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

Planetary solidarity to address climate change, overpopulation, poverty and all the other common threats to the welfare of the world may be desirable, but is wildly improbable.

From MarketWatch • May 31, 2026

“Based on the information we have, life is one of the most likely ways we could get this,” says Morgan Cable of the Planetary Science Institute, a nonprofit research institute in Arizona.

From The Wall Street Journal • Apr. 23, 2026

Adam Lewis is the head of Planetary Group, a marketing agency that produces and promoting musician showcases in the U.S., with a significant roster of artists from abroad.

From Los Angeles Times • Apr. 19, 2026

Extensive health studies were conducted on the Apollo astronauts, but technology has advanced greatly in the 50 years since, said Bruce Betts, chief scientist at the Planetary Society, a space advocacy group.

From Barron's • Apr. 10, 2026

“Yes. It was necessary, you see, since there are four Machines, one handling each of the Planetary Regions. And all four are yielding imperfect results.”

From "I, Robot" by Isaac Asimov

Related Words

• global
• terrestrial