People often confuse the adverb awhile with the noun phrase a while. This is hardly surprising because they sound the same and the noun phrase can function like an adverb. In many cases both forms are acceptable. You can say It took a while to get down the hill, where a while functions like other noun phrases such as an hour or a long time. You can also say It took awhile to get down the hill, where awhile functions like the adverb phrase quite long or the comparative adverb longer

You may want to be careful using a while after prepositions, where traditional grammar calls for a noun as object. Thus you should write I’ll stay for a while, but not I’ll stay for awhile. Without the preposition, either form is acceptable: I’ll stay a while or I’ll stay awhile