involution noun. [ɪnvǝ'lu:ʃ(ǝ)n] LME.
[Latin involutio(n-), from involut- pa. ppl stem of involvere INVOLVE: see -ION.]
1. Anatomy. A folding, curling, or turning inwards; (a part of) a structure so formed. LME.

2. a. A thing that enfolds; an envelope, a covering. L16.
b. The action of involving or fact of being involved; implicit inclusion; implication. E17.

3. Entanglement, complication; intricacy of (literary) construction or style. Also, something complicated; an intricate movement, a tangle. E17.

4. Math.
a. The raising of a quantity to any (orig., a positive) power. arch. E18.
b. Geometry. A projective correspondence between pairs of points on a line, such that the product of the distances of each pair from a certain fixed point on the line is constant. M19.
c. A function or transformation that is equal to its inverse. E20.

5. Physiology. Shrinkage, regression, or atrophy of a part or organ (esp. the uterus) when inactive, or in old age. M19.

■ involutional adjective (chiefly Psychology) of or pertaining to physiological involution or mental disturbances associated with this change;

■ involutional depression,

■ involutional melancholia, prolonged depression beginning late in life: E20.

■ involutionary adjective characterized by involution; retrograde E20.

■ involutory adjective (Math.) that is an involution M20.

[TahlilGaran] English Dictionary ▲