“anyone” vs. “any one”

Use "anyone" as a general pronoun meaning any unspecified person, and "any one" as two words when singling out a specific individual or item from a defined group, especially before "of."

The real distinction

The test that resolves this pair almost every time: if the sentence could be followed by "of them" or "of these" and still make sense, singling out one specific member of a group, you need the two-word "any one"; if the sentence is simply referring to an unspecified person in general, with no specific group being drawn from, you need the one-word "anyone." Compare "anyone can enter the contest" (any unspecified person at all, no group implied) against "any one of the contestants could win" (specifically singling out one member from the defined group of contestants). A secondary test: "anyone" can never be immediately followed by "of," while "any one" very often is — noticing whether "of" appears right after the phrase is frequently the fastest practical check. Because "anyone" is a common, everyday pronoun appearing constantly in casual questions and general statements ("has anyone seen my keys?"), while "any one" is comparatively rare and mostly shows up in more precise or formal writing emphasizing selection from a specific set, the one-word spelling is by far the safer default when a writer is unsure, since genuine sentences needing the two-word phrase are less frequent overall. This exact same one-word-versus-two-word logic governs the closely related pairs "anytime/any time" and "anybody/any body," all following the identical underlying rule: the fused compound is the general, vague pronoun or adverb, while the two-word phrase singles out something specific. Legal and contract writing tends to favor the more precise two-word "any one" specifically because contracts often need to specify exactly one item from an enumerated list ("any one of the following conditions"), where the vaguer, more casual "anyone" would actually introduce ambiguity about whether a person or an item from the list was meant, a distinction that matters far more in binding legal language than in ordinary conversation. Standardized test writing and instructional prose show the same preference for precision, often phrasing multiple-choice-style questions with "any one" specifically to signal that exactly one option from a list should be selected, rather than leaving open the vaguer possibility that any unspecified person could satisfy the condition.

Examples with “anyone”

• Anyone can sign up for the workshop online.
• Is anyone available to help with the move this weekend?
• She didn't recognize anyone at the party.
• Anyone with a valid ticket can enter the venue.
• Has anyone seen my phone charger?
• Anyone interested in volunteering should contact the office.
• I don't think anyone noticed the mistake.
• Anyone who arrives late will need to wait outside.

Examples with “any one”

• Any one of these routes will get you there on time.
• You can choose any one of the three desserts.
• Any one of the candidates would make a strong hire.
• Pick any one book from the shelf to start with.
• Any one of us could have made that same mistake.
• Any one of the applications could be approved by Friday.
• You may select any one item from the discounted rack.
• Any one of these solutions should solve the problem.

Memory trick

Check for "of" right after the phrase: if it's there ("any one of..."), keep the two words separate; if there's no "of" and the sentence is just making a general statement about an unspecified person, fuse it into "anyone." A second useful test: try swapping in "a single one" for the phrase — if that swap still makes sense, you need "any one"; if it sounds unnatural, you need the general pronoun "anyone" instead.