"Are they American?" or "Are they Americans?"
What is the difference between
Are they American?
and
Are they Americans?
Solution 1:
Both are correct and mean the same thing. The difference is that in
Are they American?
American is used as an adjective, while in
Are they Americans?
it is used as a noun in plural form. If there were only one person, the questions would become
Is he American?
and
Is he an American?
Solution 2:
Although the subject is they in both cases, Are they American? considers the group as a whole, whereas Are they Americans? considers the group as a collection of individuals.