Planet Means Wanderer
A planet orbits a star. The Greek name records what ancient observers saw: stars that moved against the fixed background.
A planet is a body orbiting a star. The name records ancient observation: Greek *planetes* means wanderer, because these points of light moved against the fixed stars night after night. The modern definition was formalised in 2006, requiring a body to orbit the sun, be round under its own gravity, and have cleared its orbital neighbourhood.
- A body orbiting a star. *An outer planet.*
- The earth. *Save the planet.*
- Planetary — of planets. *Planetary science.*
- Dwarf planet — a body not clearing its orbit. *Pluto is a dwarf planet.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | planet | A rocky planet. |
| Plural | planets | Eight planets. |
| Adjective | planetary | Planetary orbits. |
| Related | planetarium | A city planetarium. |
| Related | exoplanet | A confirmed exoplanet. |
How it is used in a sentence
- Planet means wanderer.They moved against the fixed stars.
- Pluto was reclassified in 2006.As a dwarf planet.
- Thousands of exoplanets are now confirmed.Orbiting other stars.
The 2006 definition
- Orbits the sun — not another planet
- Round — massive enough for gravity to shape it
- Cleared its orbit — dominant in its own neighbourhood
- Pluto — fails the third criterion
- Dwarf planet — the category created for such bodies
From Greek *planetes*, a wanderer, from *planasthai*, to wander. The days of the week are named after the classical planets.
Why is Pluto not a planet?
Because it has not cleared its orbital neighbourhood. It shares the Kuiper Belt with many similar bodies.
Are the days named after planets?
Yes. The Latin names survive in Romance languages, and English replaced several with Norse gods of equivalent role.