unhyphenated spelling
I have removed the  tag from the spelling note; of course this is not the sort of thing for which citations are likely to be available. It's the kind of thing you'd find in a dictionary, but no one writes dictionaries of contemporary set-theoretic usage. If you want a citation in which the spelling is used, I can find that for you once I get home (I'd put it on the talk page, not in the article).