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pregnancy

(Encyclopedia)pregnancy, period of time between fertilization of the ovum (conception) and birth, during which mammals carry their developing young in the uterus (see embryo). The average duration of pregnancy in h...

infrared astronomy

(Encyclopedia)infrared astronomy, study of celestial objects by means of the infrared radiation they emit, in the wavelength range from about 1 micrometer to about 1 millimeter. All objects, from trees and building...

Holocaust

(Encyclopedia)Holocaust hŏlˈəkôstˌ, hōˈlə– [key], name given to the period of persecution and extermination of European Jews by Nazi Germany. Romani (Gypsies), homosexuals, Jehovah's Witnesses, the disabl...

relativity

(Encyclopedia)relativity, physical theory, introduced by Albert Einstein, that discards the concept of absolute motion and instead treats only relative motion between two systems or frames of reference. One consequ...

color

(Encyclopedia)color, effect produced on the eye and its associated nerves by light waves of different wavelength or frequency. Light transmitted from an object to the eye stimulates the different color cones of the...

map

(Encyclopedia)map, conventionalized representation of spatial phenomena on a plane surface. Unlike photographs, maps are selective and may be prepared to show various quantitative and qualitative facts, including b...

states' rights

(Encyclopedia)states' rights, in U.S. history, doctrine based on the Tenth Amendment to the Constitution, which states, “The powers not delegated to the United States by the Constitution, nor prohibited by it to ...

knight

(Encyclopedia)knight, in ancient and medieval history, a noble who did military service as a mounted warrior. As the feudal system disintegrated, knight service was with growing frequency commuted into cash pay...

astronomy

(Encyclopedia)astronomy, branch of science that studies the motions and natures of celestial bodies, such as planets, stars, and galaxies; more generally, the study of matter and energy in the universe at large. ...

election

(Encyclopedia)election, choosing a candidate for office in an organization by the vote of those enfranchised to cast a ballot. In the United States, Canada, Mexico, Great Britain, and many other nations, usuall...