A tree of the species Platanus × acerifolia.

(geometry) A three-dimensional vector space over the field of real numbers in which one-dimensional linear subspaces are considered as “points” and two-dimensional linear subspaces are considered as “lines”. Equivalently, a sphere in which pairs of antipodal points are considered as “points” and great circles are considered as “lines”.

plural of London plane tree

(now historical or astrology) 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.

(astronomy) A planet which orbits in the habitable zone around a star, where temperatures like those on Earth occur, allowing for the possible existence of liquid water and of life.

The planet Uranus.

(astronomy) An asteroid of any size / (astronomy) An asteroid-like body in an orbit beyond the asteroid belt, such as a centaur or Kuiper belt object

That branch of astronomy that deals with the planets of the solar system.

the planet Mars

(astronomy) a ring of dust, moonlets and other matter that orbits a planet (such as Saturn) as a flat disc; gaps in the ring are due to the presence of shepherd moons