Blackout vs. Black Out
“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.
Use “blackout” as the noun for a loss of power/light, a reporting restriction, or a brief loss of consciousness. Use “black out” as the verb for becoming unconscious or making something dark or unreadable.
Key details
Choose the right form
| Meaning / situation | Construction | Decision |
|---|---|---|
| name an event/state such as a power loss or reporting restriction | blackout | use the closed noun |
| perform the action of losing consciousness or obscuring/darkening something | black out | use the two-word verb |
Quick tests
Noun-or-verb test
Is the expression naming a thing/event, or functioning as a verb that can change tense?
If yes: For the noun, use “blackout.”
If no: For the verb, use “black out.”
Caveat: The meanings of the noun vary by context; the spelling decision here is based on grammatical role.
Examples
The storm caused a two-hour blackout.
“Blackout” names the event.
Please black out the account number before sharing the scan.
“Black out” is the verb.
He blacked out for a few seconds.
The spaced phrasal verb takes ordinary tense inflection.
Further guidance
Core difference
Use the documented noun or modifier form when naming a thing, result, event, or concept; use the spaced form when the words function as a verb.
Fast Test
If the expression can take ordinary verb tense or inflection in the sentence, the spaced verb form is usually the relevant choice.
Variant Boundary
Cambridge distinguishes the closed noun “blackout” from the two-word phrasal verb “black out.”
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.
- Blackout — Cambridge Dictionary (opens in a new tab)Cambridge Dictionary · Closed noun “blackout” for loss of power/light, suppressed information, or brief unconsciousness
- Black out — Cambridge Dictionary (opens in a new tab)Cambridge Dictionary · Two-word phrasal verb “black out” for becoming unconscious or obscuring/darkening something