“Turn off” is the two-word phrasal verb for switching something off, leaving a road, or causing loss of interest. The corresponding noun appears as closed “turnoff” in American usage and also as hyphenated “turn-off” in Cambridge.
ReviewedEvidence2 sourcesSectionEnglish Usage
Quick answer
Use “turn off” as the phrasal verb. Use noun “turnoff” in common American spelling; Cambridge also records the hyphenated noun “turn-off.”
Key details
Confusion Familyword-boundary
Rule Familynoun versus phrasal verb
Termsturnoff, turn-off, turn off
Variant ScopeThe spaced form is the verb; noun spelling can be closed or hyphenated by variety/style.
Further guidance
Core difference
Use “turn off” when the expression is a verb; use the noun form “turnoff”/“turn-off” when naming a road exit or something that causes loss of interest.
Fast Test
If you can inflect the action as “turned off” or “turning off,” use the spaced verb.
Usage Boundary
Noun spelling varies: Cambridge shows closed “turnoff” in its American dictionary and hyphenated “turn-off” in other entries, so do not label one noun spelling universally wrong.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
“Lockdown” is the noun for an official restriction or state of restricted movement, while “lock down” is the corresponding phrasal verb. Sentence function determines the spacing.
“Phase out” and “phaseout” differ by grammatical function. Merriam-Webster records “phaseout” as the noun and “phase out” as the corresponding verb, with forms such as “phased out” and “phasing out.”
“Touchdown” and “touch down” differ mainly by grammatical function. Cambridge records the closed form as a countable noun for landing and sports senses and the two-word form as a phrasal verb, including aircraft landing and rugby uses.
Standard English writes “a lot” as two words for a large amount, number, frequency, or degree. “Alot” is a common misspelling in this sense; it should not be confused with the separate verb “allot.”
“Any more” can be a determiner for additional quantity and an adverb meaning “no longer.” Cambridge notes that the one-word adverb “anymore” is especially common in American English, while the determiner remains two words.
“Anyone” is one word when it means any person. “Any one” is written as two words when the construction refers to a single member of a larger set, including the common pattern “any one of …”.
