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e, in mathematics

(Encyclopedia)e, in mathematics, irrational number occurring widely in mathematics and science, approximately equal to the value 2.71828; it is the base of natural, or Naperian, logarithms. The number e is defined ...

earth, in chemistry

(Encyclopedia)earth, in chemistry, metallic oxide not readily reducible by chemical means, e.g., alkaline earths, rare earths, and alumina. The name is also applied to certain absorbent clays, e.g., fuller's earth,...

echidna, in zoology

(Encyclopedia)echidna ĭkĭdˈnə [key] or spiny anteater, animal of the order Monotremata, the egg-laying mammals. A short-legged, grayish brown animal, the echidna is covered with sharp quills and can protect its...

echo, in acoustics

(Encyclopedia)echo, reflection of a sound wave back to its source in sufficient strength and with a sufficient time lag to be separately distinguished. If a sound wave returns within 1⁄10 sec, the human ear is in...

eclecticism, in art

(Encyclopedia)eclecticism ĭklĕkˈtĭsĭzˌəm [key], art style in which features are borrowed from various styles. It was once applied to the Carracci, who incorporated elements from the Renaissance and classical...

eclecticism, in philosophy

(Encyclopedia)eclecticism ĭklĕkˈtĭsĭzˌəm [key] [Gr. eklektikos=to choose], in philosophy, the selection of elements from different systems of thought, without regard to possible contradictions between the sy...

depression, in economics

(Encyclopedia)depression, in economics, period of economic crisis in commerce, finance, and industry, characterized by falling prices, restriction of credit, low output and investment, numerous bankruptcies, and a ...

depression, in psychiatry

(Encyclopedia)depression, in psychiatry, a symptom of mood disorder characterized by intense feelings of loss, sadness, hopelessness, failure, and rejection. The two major types of mood disorder are unipolar disord...

Algol, in astronomy

(Encyclopedia)Algol ălˈgŏl [key], famous variable star in the constellation Perseus; Bayer designation β Persei; 1992 position R.A. 3h07.7m, Dec. +40°55′. Algol's variation in apparent magnitude, from 2.06 t...

dispersion, in chemistry

(Encyclopedia)dispersion, in chemistry, mixture in which fine particles of one substance are scattered throughout another substance. A dispersion is classed as a suspension, colloid, or solution. Generally, the par...