awhile

adverb (for) a brief period of time.

correct spelling only when used as an adverb and not in a prepositional phrase. Otherwise, in a prepositional phrase, it is two words. As a noun phrase, it is two words.

Adverb: I will wait awhile for you, but after that I'm out.

Prep Phrase: I will wait for a while, but after that I'm out.

Noun Phrase: A while has gone by since we started this project.