Speedup vs. Speed Up
“Speed up” is the verb phrase. The noun is commonly “speed-up,” with “speedup” also recorded in US English. The distinction is grammatical function, not a claim that only one noun spelling can ever occur.
Use “speed up” as a phrasal verb meaning to make or become faster. Use “speed-up” as a noun for an increase in speed or rate; Cambridge also records unhyphenated “speedup” in US English.
Key details
Choose the right form
| Grammatical role | Form | Decision |
|---|---|---|
| verb meaning make or become faster | speed up | Use the two-word phrasal verb. |
| noun meaning an increase in speed or rate | speed-up | Use the documented hyphenated noun form. |
| US noun spelling | speedup | Cambridge also records the closed noun in US English. |
Quick tests
Meaning / construction test
Is the expression functioning as the action verb?
If yes: Use “speed up.”
If no: If it names an increase in speed or rate, use a noun form such as “speed-up”; “speedup” is also documented in US English.
Caveat: The closed or hyphenated noun spelling should not be transferred to the verb phrase.
Examples
The new lane may speed up boarding.
“Speed up” is the two-word phrasal verb.
The change produced a speed-up in processing.
The hyphenated form is a documented noun.
The update produced a speedup in processing.
Cambridge also records the closed noun “speedup” in US English.
Further guidance
Core difference
“Speed up” is a phrasal verb; “speed-up” is a noun, and Cambridge also records “speedup” as a US noun spelling.
Fast Test
If you can replace the expression with a verb such as “accelerate,” write “speed up.” If you mean an increase in rate, use the noun form appropriate to your style.
Usage Boundary
Do not transfer the closed or hyphenated noun spelling to the verb phrase.
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.
- Speed (something) up — Cambridge Dictionary (opens in a new tab)Cambridge Dictionary · Dictionary evidence that both “sped” and “speeded” are documented past forms of speed, including speed up.