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biology

(Encyclopedia)biology, the science that deals with living things. It is broadly divided into zoology, the study of animal life, and botany, the study of plant life. Subdivisions of each of these sciences include cy...

zero

(Encyclopedia)zero, that number which, when added to any number, leaves the latter unchanged; its symbol is 0. The introduction of zero into the decimal system was the most significant achievement in the developmen...

rare-earth metals

(Encyclopedia)rare-earth metals, in chemistry, group of metals including those of the lanthanide series and actinide series and usually yttrium, sometimes scandium and thorium, and rarely zirconium. Promethium, whi...

Barnard, Frederick Augustus Porter

(Encyclopedia)Barnard, Frederick Augustus Porter, 1809–89, American educator and mathematician, b. Sheffield, Mass., grad. Yale, 1828. After tutoring at Yale and teaching in institutions for the deaf and mute, he...

Sanger, Margaret Higgins

(Encyclopedia)Sanger, Margaret Higgins, 1879–1966, American leader in the birth control movement, b. Corning, N.Y. Personal experience and work as a public-health nurse, much of it on New York City's Lower East S...

erosion

(Encyclopedia)erosion ĭrōˈzhən [key], general term for the processes by which the surface of the earth is constantly being worn away. The principal agents are gravity, running water, near-shore waves, ice (most...

APRA

(Encyclopedia)APRA äˈprä [key] or the Alianza Popular Revolucionaria Americana, reformist political party in Peru, also called the Partido Aprista. Founded (1924) by Victor Raúl Haya de la Torre while in exile,...

pendulum

(Encyclopedia)pendulum, a mass, called a bob, suspended from a fixed point so that it can swing in an arc determined by its momentum and the force of gravity. The length of a pendulum is the distance from the point...

Pusey, Edward Bouverie

(Encyclopedia)Pusey, Edward Bouverie pyo͞oˈzē [key], 1800–1882, English clergyman, leader in the Oxford movement. Having studied at Christ Church College, Oxford, Pusey was elected a fellow of Oriel College (1...

alkene

(Encyclopedia)CE5 Alkenes alkene ălˈkēn [key], any of a group of aliphatic hydrocarbons whose molecules contain one or more carbon-carbon double bonds (see chemical bond). Alkenes with only one double bond h...