English UsageComparison guide
Slowdown vs. Slow Down
“Slowdown” is a noun meaning a reduction in speed or activity. “Slow down” is the verb phrase meaning to reduce speed or become less active.
Use “slowdown” as a noun and “slow down” as a verb.
Key details
Confusion Familynoun versus phrasal verb
Rule Familyword boundary and part of speech
Termsslowdown, slow down
Further guidance
Core difference
“Slowdown” is a noun. “Slow down” is a verb phrase/phrasal verb.
Fast Test
If you can put “a” before it, the noun “slowdown” is likely. If someone or something performs the action, use “slow down.”
Usage Boundary
Spacing follows grammatical role here; the closed noun does not replace the two-word verb.
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.
- Slowdown — Cambridge Dictionary (opens in a new tab)Cambridge University Press · Direct noun entry for “slowdown” as a reduction in speed or activity.
- Slow down — Cambridge Dictionary (opens in a new tab)Cambridge University Press · Direct phrasal-verb entry for “slow down.”