involution

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

• noun The act of involving.
• noun The state of being involved.
• noun Intricacy; complexity.
• noun Something, such as a long grammatical construction, that is intricate or complex.
• noun Mathematics An operation, such as negation, which, when applied to itself, returns the original number.
• noun Embryology The ingrowth and curling inward of a group of cells, as in the formation of a gastrula from a blastula.
• noun A decrease in size of an organ, as of the uterus following childbirth.
• noun A progressive decline or degeneration of normal physiological functioning occurring as a result of the aging process.

from The Century Dictionary.

• noun The atrophic or regressive changes occurring in old age.
• noun In biology, the possession by an organism which is adapted to conditions that are simpler than those under which its allies live, of an organization that is simpler than that of its allies, considered as evidence of inverse or retrograde evolution.
• noun The act of involving, infolding, or inwrapping; a rolling or folding in or round.
• noun The state of being entangled or involved; complication.
• noun Something involved or entangled; a complication.
• noun A membranous covering or envelop; an involucre.
• noun In grammar, complicated construction; the lengthening out of a sentence by the insertion of member within member; the separation of the subject from its predicate by the interjection of matter that should follow the verb or be placed in another sentence.
• noun In mathematics: The multiplication of a quantity into itself any number of times, so as to produce a positive integral power of that quantity.
• noun The raising of a quantity to any power, positive, negative, fractional, or imaginary. In this sense involution includes evolution as a particular case.
• noun A unidimensional continuous series of elements (such as the points of a line), considered as having a definite one-to-one correspondence with themselves, such that infinitely neighboring elements correspond to infinitely neighboring elements, and such that if A corresponds to B, then B corresponds to A: in other words, the elements are associated in conjugate pairs, so that any pair of conjugate elements may by a continuous motion come into coincidence with any other without ceasing, at any stage of the motion, to be conjugate.
• noun Any series of pairs of loci represented by an equation λU + µ V = 0, where λ and µ are numerical constants for each locus, and U = 0 and V = 0 are equations to two loci of the same order.
• noun Any unidimensional continuum of elements associated in sets of any constant number by a continuous law. According as there are two, three, four, etc., in each set, the involution is said to be quadratic, cubic, quartic (or biquadratic), etc.
• noun The implication of a relation in a system of other relations.
• noun In physiology, the resorption which organs undergo after enlargement or distention: as, the involution of the uterus, which is thus restored to its normal size after pregnancy.

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

• noun The act of involving or infolding.
• noun The state of being entangled or involved; complication; entanglement.
• noun That in which anything is involved, folded, or wrapped; envelope.
• noun (Gram.) The insertion of one or more clauses between the subject and the verb, in a way that involves or complicates the construction.
• noun (Math.) The act or process of raising a quantity to any power assigned; the multiplication of a quantity into itself a given number of times; -- the reverse of evolution.
• noun (Geom.) The relation which exists between three or more sets of points, a.a', b.b', c.c', so related to a point O on the line, that the product Oa.Oa' = Ob.Ob' = Oc.Oc' is constant. Sets of lines or surfaces possessing corresponding properties may be in involution.
• noun (Med.) The return of an enlarged part or organ to its normal size, as of the uterus after pregnancy.

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

• noun entanglement; a spiralling inwards; intricacy
• noun mathematics An endofunction whose square is equal to the identity function; a function equal to its inverse.
• noun physiology The regressive changes in the body occurring with old age.
• noun mathematics, obsolete A power: the result of raising one number to the power of another.

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

• noun marked by elaborately complex detail
• noun a long and intricate and complicated grammatical construction
• noun the act of sharing in the activities of a group
• noun the action of enfolding something
• noun reduction in size of an organ or part (as in the return of the uterus to normal size after childbirth)
• noun the process of raising a quantity to some assigned power