"Comprises" is frequently used in patent writing, but I have rarely seen it elsewhere. I think its use, both in patents and normal English, has a particular co

"Comprises" is frequently used in patent writing, but I have rarely seen it elsewhere. I think its use, both in patents and normal English, has a particular connotation, that "is comprised of" doesn't carry otherwise: * When I hear "X comprises Y and Z," I think that the author is saying that X includes Y and Z as its key parts, but is not precluding the existence of other parts * When I hear "X is comprised of Y and Z," I think Y and Z are the only parts of X This might have originally been a misuse of the word "comprise" to mean "compose," but I feel like that's a pretty big distinction in meaning.