Function (n.) form an unordered generality, and our mathematics is built on it.
A Function (n.) is named after certain models, and whatever resembles them gets the name, which makes it a blurred concept.
Function (n.) in nature always has its shadow: whatever serves a purpose somewhere also turns up where it serves none, or even harms.
Function (n.) always means technique, whether of a word in a sentence, a game or a language: a general way of explaining and training.
A Function (n.) of a word in a sentence is nothing hidden — don't we see the whole sentence? It must come out in operating with the word.
Function (n.) in nature is never exclusive: whatever serves a purpose there also turns up where it serves none, even where it is 'dysfunctional'.