Q. In your hyphenation guide, adjectival phrases are addressed: “Hyphenated before a noun; usually open after a noun.” Would the adjectival phrase “one-on-one” apply? The dictionary lists it only with hyphens, but I’m dealing with a sentence where it seems the hyphens would be unnecessary: “Coaches are available to meet one-on-one.”
A. In your example, “one-on-one” functions as an adverb rather than as an adjective (it modifies the verb to meet). And in general, a phrase that’s listed in Merriam-Webster with hyphens retains its hyphens if used as an adverb. Compare “day by day.” That expression, which is listed in Merriam-Webster without hyphens, would be hyphenated only as an adjective before a noun. For example, you would “take things day by day” (adv.) but “make a day-by-day assessment” (adj.).