2 Answers

Depends on the context of the sentence. 

Tom had to wait awhile for Sally to get home. 

Every once in a while, Sally came home late. 

"A While" Versus "Awhile"

by Mignon Fogarty 

What is the difference between "a while" and "awhile"?

"A while" is a time, a noun. The article "a" before "while" is a sure sign that you're dealing with a noun. Notice in the following sentence that you could replace "a while" with another article-noun combination such as "a year":

It's been a while since Squiggly tried marmite.

"Awhile" means "for a time" and it's an adverb. Notice in the following sentence that you could replace "awhile" with another adverb such as "quietly":

Go play awhile.

Finally, just to make it confusing, if you rephrase the previous sentence and replace the adverb with a prepositional phrase, you need the noun again because an adverb can't be the object of the preposition.

Go play for a while.