A natural number is a positive whole number.

Natural numbers are sometimes called positive or non-negative integers.

For example, 3, 16, 512, and 1,382,437 are all considered natural numbers. -2, 4.25, and 18,512.5 are not.

The number zero may or may not be considered a natural number, depending on the definition of natural number being used.

For instance, if natural numbers are defined as non-negative integers, then zero can be considered a natural number (0, 1, 2, 3, 4...).

But if natural numbers are defined as positive integers, then zero is not considered a natural number (1, 2, 3, 4...).

In computer science, some standards like ISO 80000-2 define zero as a natural number.