A preposition must have a noun or pronoun as its object. If there is no object, we don't
call the word a preposition.
...She took it OUT. ("Out" is an adverb.)
...She too it OUT the door. ("Out" is a preposition.)
...I had not seen her BEFORE. ("Before" is an adverb.)
...I had not seen her BEFORE Friday. ("Before" is a preposition.)
When "awhile" is one word, it is an adverb; when it is two words, it is a noun. Thus it has
to be "a while" when it is part of a prepositional phrase.
...He left for a while.
...I will be there in a while.
More to come tomorrow.
Happy punctuating!
Margie