Most words function properly because we more or less agree on what they mean. I can say "chair" and you will most likely have a good idea of what I am talking about. There are other terms, however, where people seem to squabble quite a bit about what a term actually means - like "art", "personhood", "fairness", etc. My question is: Can such terms be useful even if there are several opposing interpretations of what they mean? How? No doubt the debate itself is informative, but if we don't have a clear understanding of what "art" means, I wonder how useful it is to talk about the qualities of art, the study of art, or whether something counts as art. So how useful are terms where people can't agree on a concrete meaning? When does a term become too vague or disputed to be useful?