Turn-on vs. Turn On
The spaced form “turn on” functions as a phrasal verb. The noun meaning a person or thing that excites or attracts is commonly written “turn-on”; Collins additionally records a closed American-English noun “turnon,” so the page keeps that variation explicit.
Use “turn on” as the phrasal verb. For the informal noun, “turn-on” is a standard dictionary form; Collins also records closed “turnon” in American English.
Key details
Choose the right form
| Context | Use | Decision |
|---|---|---|
| verb meaning activate or switch on | turn on | Use the two-word phrasal verb. |
| informal noun for something attractive or exciting | turn-on | Use the hyphenated dictionary noun form. |
| American noun spelling encountered as one word | turnon | Recognize the documented closed variant rather than confusing it with the verb. |
Quick tests
Word-class test
Is the expression functioning as a verb?
If yes: Write “turn on” as two words.
If no: For the informal noun, “turn-on” is a standard form; a closed “turnon” variant is also documented in American English.
Caveat: The noun is informal and is not interchangeable with every verbal sense of “turn on.”
Examples
Please turn on the lamp before you leave.
“Turn on” is the two-word phrasal verb.
Confidence can be a turn-on for some people.
“Turn-on” is the informal noun form.
The editor kept turn-on as the noun and turn on as the verb.
The spelling difference follows word class.
Further guidance
Core difference
Use “turn on” as a phrasal verb. Use the noun form “turn-on” when naming something that excites or attracts; Collins also records closed “turnon” in American English.
Fast Test
If you can inflect the action as “turned on” or “turning on,” use the two-word verb. If it functions as a noun, use a dictionary-recorded noun form.
Usage Boundary
The noun is informal/slang in the attraction/excitement sense, and noun spelling varies by dictionary/variety; do not claim the closed noun is universally impossible.
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.
- Turn on / turn-on — Collins English Dictionary (opens in a new tab)HarperCollins Publishers · Dictionary evidence distinguishing phrasal verb “turn on” from noun “turn-on”; Collins also records closed “turnon” in American English.