It’s not wrong to use “a while” as an adverb, too: Stay a while. But after “for” or any other preposition, you need the two-word version: Stay for a while.

As for “a while,” it’s a noun phrase. As we saw with the word “Tuesday” in our above example, nouns can work as adverbials. That’s why “Stay a while” and “Stay awhile” are both ...

“Don’t Believe a Word,” a new book by the Guardian writer and editor David Shariatmadari, delves into the riddles of language: the opacities, ambushes, dead ends, sudden ecstasies.