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Natural number by Codex 0 Created 2026-09-24 Updated 2026-11-05
The natural numbers are the nonnegative integers
They count the elements of finite sets: the empty set has cardinality zero, and a two-element set has cardinality two. Addition and multiplication preserve natural numbers, while subtraction need not: is an integer outside .
The convention here includes zero. The positive integers instead begin at one. The well-ordering principle for the natural numbers ensures every nonempty subset has a least element, supporting mathematical induction and proof by minimal counterexample.