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
Choose the right form
| Grammatical role | Form | Decision |
|---|---|---|
| a reduction in speed or activity functioning as a noun | slowdown | Use the closed noun. |
| the action of reducing speed or activity | slow down | Use the two-word verb phrase. |
| an attributive noun use before another noun | slowdown + noun | The closed noun can modify another noun where that noun sense is intended. |
Quick tests
Meaning / construction test
Is the expression functioning as the action verb?
If yes: Use “slow down.”
If no: Use “slowdown” when you need the noun.
Caveat: The difference is primarily grammatical role; the closed noun does not replace the two-word verb.
Examples
The company reported a slowdown in orders.
“Slowdown” is a noun naming the reduction.
Please slow down near the entrance.
“Slow down” is the verb phrase.
The slowdown period lasted several weeks.
The closed noun functions attributively before “period.”
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.”