#computer-arithmetic ## Definition > [!tldr] Definition > A **natural number** is any non-negative [[Integers|integer]]. That is, a natural number is any number from the list $0, 1, 2, 3, \dots$. The set of all natural numbers is denoted $\mathbb{N}$. While [[integers]] form the backbone of all computer mathematics, the natural numbers are a subset of the [[integers]] and are the primary tool used for counting things. For example, Python uses the natural numbers for the function `range` which is used to iterate through looping structures. Note that **for our purposes, the number $0$ is included in the natural numbers**. This is not always the case in every textbook or learning resource. So when looking up information in other books or websites about natural numbers or statements involving natural numbers, *check first to see if they include 0.* ## Examples and Non-Examples Some examples of natural numbers include $10$, $99999$, and $0$. Some examples of non-natural numbers include: - $-12$ (negative) - $1/2$ (not a whole number) - $\sqrt{5}$ (also not a [[Integers|whole number]]) - $2 + 3i$ (not a real number) - $\infty$ (not a number at all) ## Resources - [Wikipedia article on natural numbers](https://en.wikipedia.org/wiki/Natural_number) - [Python documentation on `range`](https://docs.python.org/3/library/functions.html#func-range)