Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
acceptance, acceptation (nn.)
Acceptance is the word in far more general use; it means “the act of accepting” in all the senses of the word. Acceptation is mostly a much more specialized linguistic term, meaning “the usual or accepted version of an idea or meaning of a word,” and it has been labeled archaic when used to mean “acceptance.”
