"Whole numbers" are often referred to without being defined, since many people think everyone knows what they are.
However, there are at least three things people mean by the term.
Positive integers Non-negative integers Integers
It is possible to find maths homeworks on the web where students are asked which numbers on a list are whole numbers, and to find model answers where, for example, -3 is not one.
If you say "whole numbers", it may be best to say what you mean by it. Or don't use it at all.
It's quite easy to find books which use the term without defining it explicitly. If someone says the powers of x in a polynomial have to be whole numbers, that's a pretty good clue as to what they think it means.