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Proteus, in astronomy

(Encyclopedia)Proteus prōˈtēəs, –tyo͞os [key], in astronomy, one of the natural satellites, or moons, of Neptune. ...

pyramid, in geometry

(Encyclopedia)CE5 Pyramid pyramid, in geometry, solid figure bounded by a polygon (the base, or directrix) and the surface generated by a moving line (the generator) passing through a fixed point (vertex) and c...

quadrant, in technology

(Encyclopedia)quadrant, in technology, angle-measuring device based on a scale of 90°. It is sometimes confused with the sextant, a similar instrument based on a scale of 60°. The quadrant is rarely used today. ...

Rhea, in astronomy

(Encyclopedia)Rhea, in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn V (or S5), Rhea is 950 mi (1530 km) in diameter, orbits Saturn at a mean distance of 327,487 mi (527,...

ring, in astronomy

(Encyclopedia)ring, in astronomy, relatively thin band of rocks and dust and ice particles that orbit around a planet in the planet's equatorial plane. All four of the giant planets in the solar system—Jupiter, S...

nucleus, in biology

(Encyclopedia)nucleus: see cell, in biology.

nucleus, in physics

(Encyclopedia)nucleus, in physics, the extremely dense central core of an atom. Following the discovery of radioactivity by A. H. Becquerel in 1896, Ernest Rutherford identified two types of radiation given off b...

nun, in religion

(Encyclopedia)nun: see monasticism.

nut, in botany

(Encyclopedia)nut, in botany, a dry one-seeded fruit which is indehiscent (i.e., does not split open along a definite seam at maturity). Among the true nuts are the acorn, chestnut, and hazelnut. Commonly the word ...

nimbus, in art

(Encyclopedia)nimbus nĭmˈbəs [key], in art, the luminous disk or circle or other indication of light around the head of a sacred personage. It was used in Buddhist and other Asian art and by the early Greeks and...