involution

From Latin involūtiō, from involvō.

• IPA^(key): /ɪnvəˈluːʃən/
• Rhymes: -uːʃən

involution (countable and uncountable, plural involutions)

1. Entanglement; a spiralling inwards; intricacy.
   • 1938, Xavier Herbert, Capricornia, chapter V, page 74,

     […] usually his attention was diverted from her feet by her shrieks of laughter and the astounding involutions of her huge brown-yellow frame.

   • 1968, Anthony Burgess, Enderby Outside, 2002, The Complete Enderby, page 302,

     ‘Gomez,’ said the mortician, ‘is an expert only on the involutions of his own rectum.’

2. A complicated grammatical construction.
   • 1917, James Huneker, Unicorns, New York: Scribner, Chapter 11 “Style and Rhythm in English Prose,” p. 129,

     Walter Pater’s essay on Style is honeycombed with involutions and preciosity.

3. (mathematics) An endofunction whose square is equal to the identity function; a function equal to its inverse.

   Hyponyms: complex conjugation, complementation

   • 1996, Alfred J. Menezesm, Paul C. van Oorschot, Scott A. Vanstone, Handbook of Applied Cryptography, CRC Press, page 10,

     Involutions have the property that they are their own inverses.

4. (medicine) The shrinking of an organ (such as the uterus) to a former size.
5. (physiology) The regressive changes in the body occurring with old age.
6. (mathematics, obsolete) A power: the result of raising one number to the power of another.

• involution algebra

• involutional
• involutionary

• dual
• selfdual