Q. I am editing a medical index using the “word-by-word” system, and having some trouble with hyphenated words. Some terms, like “non-ionic,” feature a hyphenated word that is not a compound word. Does “non-ionic” come before “nonclostridial?” Also, do hyphenated compound words like “arterial-gas” come before or after a non-hyphenated compound word like “arterial oxygen?” Thanks—this is giving me a headache!

A. Ignore the hyphen after a prefix when indexing. “Non-ionic” should be alphabetized as though it were “nonionic,” in the way that the hyphenated compound “new-fangled” comes between “newel” and “Newfoundland” in CMOS 16.61 in the “Word by Word” column. (Note, however, that Chicago style does not normally hyphenate prefixes, following Merriam-Webster, and would thus avoid that problem.) Hyphenated compounds come after all the open ones. (Again, see 16.61, where “new-fangled” comes after “new town,” etc.)