whole number
A whole number is a counting number with one extra guest invited to the party: zero. So instead of starting at 1, the list begins at 0 and continues 0, 1, 2, 3, 4, and onward. Whole numbers are the natural numbers plus the idea of “none.”
Including zero matters because zero is a real, useful quantity — it is how we record an empty box, a balance of nothing owed, or a starting point before anything happens. Whole numbers have no fractions and no negatives; every whole number is a clean, undivided amount that is either zero or positive.
Like the natural numbers, whole numbers are closed under addition and multiplication but not under subtraction (3 − 7 leaves the set) or division (5 ÷ 2 leaves the set). The phrase “whole number” is mostly a school-level term; in higher mathematics people usually speak instead of the non-negative integers, written as the integers that are 0 or greater.
A score in a game before anyone plays is 0, a whole number. After three points it is 3 — both 0 and 3 are whole numbers.
Zero is the whole number the naturals leave out.
The only difference between the natural numbers (as we use them, starting at 1) and the whole numbers is the single element 0.