Build-up vs. Buildup vs. Build Up
“Build up” is the two-word phrasal verb. For the noun, Cambridge records hyphenated “build-up,” while its American dictionary also records closed “buildup.” The noun spelling therefore has a documented regional/style variant rather than one universal form.
Use “build up” for the verb. For the noun, “build-up” is standard in Cambridge’s main entry and “buildup” is also recorded in American English.
Key details
Choose the right form
| Meaning / situation | Construction | Decision |
|---|---|---|
| verb meaning accumulate, increase, or develop | build up | write as two words |
| noun referring to an accumulation or gradual increase | build-up | standard hyphenated noun in the reviewed main entry |
| American-English noun variant | buildup | recorded one-word noun |
Quick tests
Word-class test
Is the expression functioning as a verb?
If yes: Write “build up.”
If no: If it is a noun, use the noun spelling preferred by your variety or house style: “build-up” or recorded US “buildup.”
Caveat: Do not convert a noun spelling preference into a universal correctness claim.
Examples
Pressure can build up behind the valve.
The phrasal verb is written as two words.
There was a gradual build-up of traffic.
The hyphenated form is a standard noun spelling.
The buildup of traffic delayed deliveries.
The one-word noun is also recorded in American English.
Further guidance
Core difference
Use two words for the verb: “Pressure can build up.” Use a noun spelling when naming the accumulation or preparation period.
Fast Test
If the phrase can take tense—“built up,” “building up”—you are using the verb and should write two words.
Variant Boundary
Cambridge records hyphenated “build-up” in its main entry and closed “buildup” in its American dictionary, so the noun boundary is not a universal right-versus-wrong distinction.
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.
- Build (someone/something) up — Cambridge Dictionary (opens in a new tab)Cambridge University Press · Hyphenated noun build-up and two-word phrasal verb build up
- Buildup — Cambridge Dictionary (US) (opens in a new tab)Cambridge University Press · Closed American noun spelling buildup