a while / awhile
The noun phrase a while versus the adverb awhile.
Use a while after a preposition (for a while, in a while, after a while). Use awhile only as an adverb meaning “for a short time,” and only when no preposition is present. When in doubt, write a while.
Examples
UseStay awhile.
UseStay for a while.
AvoidStay for awhile.
UseIt has been a while since we spoke.
After a preposition, write a while: for a while, in a while, after a while. After the or this, write while: all the while, all this while.