planet

Etymology
From, from , from , , from , from , of unknown origin. Cognate with 🇨🇬, 🇨🇬, and 🇨🇬. More at. So called because they have apparent motion, unlike the "fixed" stars. Originally including also the moon and sun but not the Earth; modern scientific sense of "world that orbits a star" is from 1630s in English. The Greek word is an enlarged form of, also "wandering star, planet", in medicine "unstable temperature."

Noun

 * 1)  Each of the seven major bodies which move relative to the fixed stars in the night sky—the Moon, Mercury, Venus, the Sun, Mars, Jupiter and Saturn.
 * 2)  Any body that orbits the Sun, including the asteroids (as minor planets) and sometimes the moons of those bodies (as satellite planets)
 * 3)  A body which is massive enough to be in hydrostatic equilibrium (generally resulting in being an ellipsoid) but not enough to attain nuclear fusion and, in IAU usage, which directly orbits a star (or multiple star) and dominates the region of its orbit; specifically, in the case of the Solar system, the eight major bodies of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
 * 1)  Any body that orbits the Sun, including the asteroids (as minor planets) and sometimes the moons of those bodies (as satellite planets)
 * 2)  A body which is massive enough to be in hydrostatic equilibrium (generally resulting in being an ellipsoid) but not enough to attain nuclear fusion and, in IAU usage, which directly orbits a star (or multiple star) and dominates the region of its orbit; specifically, in the case of the Solar system, the eight major bodies of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
 * 1)  A body which is massive enough to be in hydrostatic equilibrium (generally resulting in being an ellipsoid) but not enough to attain nuclear fusion and, in IAU usage, which directly orbits a star (or multiple star) and dominates the region of its orbit; specifically, in the case of the Solar system, the eight major bodies of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
 * 1)  A body which is massive enough to be in hydrostatic equilibrium (generally resulting in being an ellipsoid) but not enough to attain nuclear fusion and, in IAU usage, which directly orbits a star (or multiple star) and dominates the region of its orbit; specifically, in the case of the Solar system, the eight major bodies of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Usage notes

 * The term planet originally meant any star which wandered across the sky, and generally included comets and the Sun and Moon. With the Copernican revolution, the Earth was recognized as a planet, and the Sun was seen to be fundamentally different. The Galilean satellites of Jupiter were at first called planets (satellite planets), but later reclassified along with the Moon. The first asteroids were also considered to be planets, but were reclassified when it was realized that there were a great many of them, crossing each other's orbits, in a zone where only a single planet had been expected. Likewise, Pluto was found where an outer planet had been expected, but doubts were raised when it turned out to cross Neptune's orbit and to be much smaller than the expectation required. When Eris, an outer body more massive than Pluto, was discovered, the International Astronomical Union (IAU) officially defined the word planet as above. However, a significant number of astronomers reject the IAU definition, especially in the field of planetary geology. Some are of the opinion that orbital parameters should be irrelevant, and that either any equilibrium (ellipsoidal) body in direct orbit around a star is a planet (there are likely at least a dozen such bodies in the Solar system) or that any equilibrium body at all is a planet, thus re-accepting the Moon, the Galilean satellites and other large moons as planets, as well as rogue planets.

Hypernyms

 * planemo

Etymology

 * ultimately from and.

Noun

 * 1)  a

Etymology
From, from , from.

Noun

 * a

Etymology 1
From, from , from.

Noun

 * a

Etymology 1
Ultimately from.

Etymology
Borrowed from.