“Burnout” is the noun for a state of severe exhaustion or, in other senses, a result/failure; “burn out” is the phrasal verb for becoming exhausted, ceasing to burn, or failing from heat. The spacing follows grammatical function rather than a single spelling preference.
ReviewedEvidence2 sourcesSectionEnglish Usage
Quick answer
Use “burnout” as the noun and “burn out” as the phrasal verb. Write “burnout” for the condition; write “burn out” when someone or something undergoes the action/process.
Key details
Confusion Familyword-boundary
Rule Familyphrasal verb versus noun
Termsburnout, burn out
Variant ScopeCambridge records closed “burnout” as a noun and spaced “burn out” as a phrasal verb; “burn-out” also occurs as a noun variant.
Further guidance
Core difference
Use “burnout” when the expression is a noun, especially for severe exhaustion. Use “burn out” when it functions as a verb.
Fast Test
If you can put an article or adjective before it (“a burnout risk,” “severe burnout”), the noun is closed. If it carries tense or follows a subject as an action (“they burn out”), use two words.
Usage Boundary
The noun may also appear as hyphenated “burn-out” in some varieties; that variant does not turn the two-word phrasal verb into a noun spelling.
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.
“Shakedown” is a noun, including senses involving extortion, a thorough search, or a testing/settling period. “Shake down” is the corresponding phrasal verb for extorting, searching, or becoming established. The one-word/two-word choice tracks grammatical function.
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 …”.
“Blackout” is the closed noun, while “black out” is the two-word phrasal verb. The verb can describe losing consciousness or obscuring/darkening something; the noun names the resulting event or state.
“Blowout” is a closed noun for several events or results, and Cambridge also records “blow-out” as a noun variant. “Blow out” is the two-word phrasal verb, including the sense of extinguishing a flame.
