“Warm up” is the phrasal verb. “Warm-up” is the established hyphenated noun for preparation before an activity, while Cambridge also records “warmup” as a noun variant.
ReviewedEvidence1 sourceSectionEnglish Usage
Quick answer
Use “warm up” as the verb. Cambridge records “warm-up” as the noun and also documents closed “warmup” as a noun variant.
Key details
Confusion Familyword-boundary
Noun Variant ScopeThe verb stays open as “warm up”; the noun is “warm-up,” with “warmup” also documented as a noun variant.
Rule Familyorthographic-boundary
Termswarm-up, warmup, warm up
Choose the right form
Decision table for Warm-up vs. Warmup vs. Warm Up
If you mean / need
Use
Why
an action such as preparing before exercise
warm up
The phrasal verb is two words.
the preparatory activity as a noun
warm-up / warmup
Cambridge records the hyphenated noun and also a closed noun variant.
Further guidance
Core difference
“Warm up” is the phrasal verb. “Warm-up” is the established hyphenated noun for preparation before an activity, while Cambridge also records “warmup” as a noun variant.
Fast Test
Choose by meaning, grammatical function, and documented regional convention rather than treating every visible variant as an error.
Variant Boundary
The verb stays open as “warm up”; the noun is “warm-up,” with “warmup” also documented as a noun variant.
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.
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“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.
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