Planet

Part of speech: noun

Pronunciation: /ˈplænɪt/

Definitions

1. A large celestial body that orbits a star and has cleared its orbital path of other debris
2. A celestial object that is massive enough to be rounded by its own gravity, orbits a star, and lacks the characteristics of a star or moon
3. A significant astronomical entity that revolves around a star, possesses sufficient mass for a nearly round shape, and has no activity as a star or a satellite

Etymology: Ancient Greek astronomers called these bodies "wanderers" because, unlike the fixed stars that kept their positions relative to one another, they seemed to drift across the night sky. The Greek "planḗtēs" was a shortened form of "astéres planêtai," meaning "wandering stars," and it came from a verb meaning "to wander about, stray." Its ultimate origin is unknown, though it shares roots with Latin "pālor," meaning "to wander about." The sense of the word has shrunk considerably over the centuries. Originally the category included the Sun and Moon, but not the Earth, which was assumed to be the fixed centre of the universe. English speakers adopted the word through Old French and Latin in the Middle Ages, and it replaced the native Old English term "tungol," which meant something like "star" or "heavenly body." The modern scientific meaning, a world that orbits a star, only appeared in English in the 1630s. That shift reversed the old logic entirely: the Earth itself now counts as a planet, while the Sun and Moon do not.

Synonyms: world, celestial body, sphere, astro, orb

Antonyms: moon, satellite, asteroid, comet, star