Is the set of whole numbers closed under subtraction?

Question

Is the set of whole numbers closed under subtraction?

Answer 1

It depends how you define "whole number." There are three possibilities. The most common is the set of non-negative integers. In this case, no, it is not closed, since 3 - 7 = -4.

Other possible definitions are positive integers (not closed) and integers (closed).

Answer 2

No

for example zero (4/0)