differentiation

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The act or process of differentiating.
• noun The state of becoming differentiated.
• noun Mathematics The process of computing a derivative.
• noun Biology The process by which cells or tissues undergo a change toward a more specialized form or function, especially during embryonic development.

from The Century Dictionary.

• noun In geology, the general process by which a parent mass of molten rock of intermediate composition, standing in a reservoir for long periods of time, breaks up or differentiates into several fractional derivatives both more acidic and more basic.
• noun The formation of differences or the discrimination of varieties.
• noun Specifically Any change by which something homogeneous is made heterogeneous, or like things are made unlike; especially, in biology, the evolutionary process or result by which originally indifferent parts or organs become differentiated or specialized in either form or function; structural or functional modification; specialization.
• noun In logic, discrimination; the act of distinguishing things according to their respective differences.
• noun In mathematics, the operation of finding the differential or differential coefficient of any function.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of differentiating.
• noun (Logic) The act of distinguishing or describing a thing, by giving its different, or specific difference; exact definition or determination.
• noun (Biol.) The gradual formation or production of organs or parts by a process of evolution or development, as when the seed develops the root and the stem, the initial stem develops the leaf, branches, and flower buds; or in animal life, when the germ evolves the digestive and other organs and members, or when the animals as they advance in organization acquire special organs for specific purposes.
• noun (Metaph.) The supposed act or tendency in being of every kind, whether organic or inorganic, to assume or produce a more complex structure or functions.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The act of differentiating.
• noun The act of distinguishing or describing a thing, by giving its different, or specific difference; exact definition or determination.
• noun The gradual formation or production of organs or parts by a process of evolution or development, as when the seed develops the root and the stem, the initial stem develops the leaf, branches, and flower buds; or in animal life, when the germ evolves the digestive and other organs and members, or when the animals as they advance in organization acquire special organs for specific purposes.
• noun geology The process of separation of cooling magma into various rock types.
• noun calculus The process of determining the derived function of a function.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a discrimination between things as different and distinct
• noun (biology) the structural adaptation of some body part for a particular function
• noun the mathematical process of obtaining the derivative of a function