which letters are nonconvex (concave) polygons?

Answer 1

You should be doing this yourself....

w, e, t, y, l, k, m, n, h, f, x, z, v

(By the way, they should all be in capitals, not lowercase letters)

Answer 2

I don't think there are any because I polygon is a closed shape. All the letters that are closed are not concave.

The answer above is clearly not right.