I don't quiet understand the concept of even, odd and neither functions.

Test to see if each function below is even, odd or neither.

What makes a functionNEITHER?

I somewhat grasp the odd and even idea (somewhat) but what actually makes it neither?

(1) f(x) = 2x + 5

(2) y = x^3 - 7

(3) h(x) = -5x^5 + 3x^4