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(Encyclopedia)diet, food and drink regularly consumed for nourishment. Nutritionists generally recommend eating a wide variety of foods; however, some groups of people survive on a very limited diet. The traditiona...

dike, in technology

(Encyclopedia)dike, in technology: see levee.

dimension, in mathematics

(Encyclopedia)dimension, in mathematics, number of parameters or coordinates required locally to describe points in a mathematical object (usually geometric in character). For example, the space we inhabit is three...

dimension, in physics

(Encyclopedia)dimension, in physics, an expression of the character of a derived quantity in relation to fundamental quantities, without regard for its numerical value. In any system of measurement, such as the met...

Dione, in astronomy

(Encyclopedia)Dione dīōˈnē [key], in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn IV (or S4), Dione is 695 mi (1,120 km) in diameter, orbits Saturn at a mean distanc...

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...