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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,...

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...

Draco, in astronomy

(Encyclopedia)Draco [Lat.,=the dragon], northern constellation lying SE of Ursa Minor and N of Lyra and Hercules. It is traditionally depicted as a dragon. Draco contains the bright star Eltanin (Gamma Draconis). T...

draft, in banking

(Encyclopedia)draft, in banking, order by one party to another party to pay a stated sum to the person or firm in whose favor the draft is made. It is similar in form to the ordinary bank check. Often the drawer an...

antipodes, in geography

(Encyclopedia)antipodes [Gr.,=having feet opposite], people or places diametrically opposite on the globe. Thus antipodes must be separated by half the circumference of the earth (180°), and one must be as far nor...

hyacinth, in botany

(Encyclopedia)hyacinth, any plant of the genus Hyacinthus, bulbous herbs of the family Liliaceae (lily family) native to the Mediterranean region and South Africa. The common, or Dutch, hyacinth of house and garden...

Hyades, in astronomy

(Encyclopedia)Hyades hīˈədēz [key], in astronomy, open star cluster in the constellation Taurus, located immediately to the right of the bright star Aldebaran. The cluster is about 130 light-years from the eart...

Hydra, in astronomy

(Encyclopedia)Hydra, in astronomy, southern constellation lying S of Corvus, Crater, Virgo, Leo, and Cancer. It is a long, slender, winding constellation traditionally depicted as a snake and known also as the Wate...
 

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