an act or instance of involving or entangling; involvement.

the state of being involved.

something complicated.

Botany, Zoology .

a rolling up or folding in upon itself.

a part so formed.

Biology . retrograde development; degeneration.

Physiology . the regressive changes in the body occurring with old age.

Grammar . a complex construction in which the subject is separated from its predicate by intervening clauses or phrases.

Mathematics . a function that is its own inverse.