in·vo·lu·tion
See also:
various esoteric brands based on the word, all of them quite different in meaning. noun
noun: involution; plural noun: involutions
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1.
Physiology
the shrinkage of an organ in old age or when inactive, e.g., of the uterus after childbirth. [ see Wikipedia] -
2.
Mathematics
a function, transformation, or operator that is equal to its inverse, i.e., which gives the identity when applied to itself. -
3.
formal
the process of involving or complicating, or the state of being involved or complicated.
"periods of artistic involution"