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

• 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

The Kent Kresa Space Gallery will feature a wide array of spacecraft, planetary probes, telescopes and more.

From Los Angeles Times • Apr. 13, 2026

“We don’t know because it’s never been done at a planetary scale before,” Webb says.

From The Wall Street Journal • Apr. 6, 2026

This suggests that electrical activity driven by dust, lightning, or energetic particles may play a broader role in shaping planetary environments.

From Science Daily • Apr. 5, 2026

Noah Petro, head of NASA's planetary geology lab, told AFP that the Moon will look to the astronauts "about the size of a basketball held at arm's length."

From Barron's • Apr. 5, 2026

Even this may be an accurate prophecy: If the planet ever is terraformed, it will be done by human beings whose permanent residence and planetary affiliation is Mars.

From "Cosmos" by Carl Sagan

Related Words

• global
• terrestrial