Both of these terms are expressions of time, but one is written with a space while the other is one word. What are the differences in meaning between the two? And what are the appropriate uses of each?
These two terms represent different parts of speech. The two-word expression a while is a noun phrase, consisting of the article a and the noun while, defined as “a period or interval of time.”
The one-word awhile is an adverb that means “for a short time or period.”
Although these definitions are similar, and although the terms can sometimes be used interchangeably, there are a few simple rules that prove helpful in keeping them straight.
The noun phrase a while can and often does follow a preposition, such as for or in: “He said he would be home in a while.”
The adverb awhile cannot follow a preposition, a rule that makes sense if you revisit the definition of the term and drop it into a sentence such as the one above: “He said he would be home in for a short time or period.” However, if we omit the preposition and rewrite it as “He said he would be home awhile,” the sentence works with a slightly altered meaning.