Integers:

Integers can be represented by the following set:

I = {..., -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, ...}

The set of integers can be broken down to the following:

Zero is neither positive nor negative.

Notice: the difference between positive integers and non-negative integers is only the zero. The difference between negative integers and non-positive integers is, also, the zero.