function(noun) a formal or official social gathering or ceremony. "it was a black-tie function". Synonyms: routine, map, single-valued function, social function, use, procedure, mathematical function, subroutine, role, affair, part, subprogram, occasion, office, purpose, social occasion, mapping. Antonyms:Is functionality a word?
The word "functionality" certainly is one of those words that were made up at a time when someone discovered the word "confidentiality" (and probably made up that ending too). Something may affect the function of something else. If something is working well it is functioning well. Function refers to the purpose of something.