Anyone or any one?
Are they interchangeable? Or do they have different meanings and uses?
We are talking about the English language, are we not? So, yes, of course, they are different and can cause confusion.
Anyone means the same thing as anybody, so if you can substitute anybody, you can use anyone as one word. Of course, why not just use anybody!
Any one cannot be replaced with anybody. Any one really means any one of them. You will notice that when any one is the correct choice, you will probably pause between the two words.
Here are some examples of the two used correctly:
I can’t find anyone to unlock the door. (You could substitute anybody.)
Any one of the managers can help you open the door. (Any one of them. You can’t substitute anybody here. It won’t make sense. Anybody of the managers?????)
Did anyone eat all the pizza that was in the kitchen?
I would have tried any one of the pizzas if I had found them.