Turn off / switch off / Off
Regional usageIn standard formal English, off is normally an adjective, adverb or preposition rather than the ordinary transitive verb for stopping a device. Use turn off or switch off.
Turn off / switch off
Use when
You use the standard verb phrase meaning stop a device, light, tap or system from operating.
Example
“Please turn off the projector after the meeting.”
Off
Use when
Avoid using off alone as a transitive verb in formal standard English when turn off or switch off is meant.
Example
“Replace 'please off the projector' with 'please turn off the projector'.”
Quick check
off the light, off the tap, off the projector, please off
Usage note
Using off as a verb in this sense is familiar in Singapore English, so the guidance is about formal standard usage rather than intelligibility.