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fatigue, in physiology

(Encyclopedia)fatigue, in physiology, inability to perform reasonable and necessary physical or mental activity. Muscle fatigue, for example, results when the contractile properties of muscle are reduced, and conti...

Epimetheus, in astronomy

(Encyclopedia)Epimetheus, in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn XI (or S11), Epimetheus is an irregularly shaped (nonspherical) body measuring about 89 mi (144...

Eris, in astronomy

(Encyclopedia)Eris, in astronomy, the largest known dwarf planet. Eris, whose highly eccentric elliptical orbit ranges from 38 AU to 97 AU and is inclined more than 44°, is the largest known object of the Kuiper b...

Eros, in astronomy

(Encyclopedia)Eros, in astronomy: see asteroid. ...

fox, in zoology

(Encyclopedia)fox, carnivorous mammal of the dog family, found throughout most of the Northern Hemisphere. It has a pointed face, short legs, long, thick fur, and a tail about one half to two thirds as long as the ...

Islam in Africa

(Encyclopedia)Islam in Africa, the development of the Muslim religion on the African continent. During Muhammad's lifetime a group of Muslims escaped Meccan persecution (615) by fleeing to Ethiopia, where the Negus...

apostrophe, in punctuation

(Encyclopedia)apostrophe: see punctuation; abbreviation. ...

Io, in astronomy

(Encyclopedia)Io īˈō [key], in astronomy, one of the 39 known moons, or natural satellites, of Jupiter. Io is subject to Jupiter's enormous tidal forces and is, as a result, the most volcanically active body in ...

ion, in chemistry

(Encyclopedia)ion, atom or group of atoms having a net electric charge. Ionization has many applications. Vapor lamps and fluorescent lamps take advantage of the light given off when positive ions recombine with ...

iris, in anatomy

(Encyclopedia)iris: see eye.