Q. The hyphenation guide at CMOS 7.96 (in sec. 2, under “adjective + noun”) lists “a top-ten school” as containing a compound modifier that needs a hyphen. But would “top ten” always be considered a compound modifier when it appears in front of a noun? For example, in the case of “the top ten schools on the list” (or any construction of “the top ten schools”), would you still recommend hyphenating?
A. That’s a very good question! A top-ten school means a school that is among the top ten schools on a ranked list. In the first expression, top-ten is a compound modifier and is therefore hyphenated; in the second, the phrase top ten simply means first ten, so no hyphen is needed.
Only rarely would the phrase the top ten schools need a hyphen, as when top-ten is being used as a category—a scenario that would be more likely with singular school: Harvard, the top-ten school most commonly selected by students planning to major in political science, is in Cambridge.