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
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.