# Is 00 a natural number?

Is there a consensus in the mathematical community, or some accepted authority, to determine whether zero should be classified as a natural number?

It seems as though formerly $0$ was considered in the set of natural numbers, but now it seems more common to see definitions saying that the natural numbers are precisely the positive integers.

Simple answer: sometimes yes, sometimes no, it’s usually stated (or implied by notation). From the Wikipedia article:

In mathematics, there are two
conventions for the set of natural
numbers: it is either the set of
positive integers $\{1, 2, 3, \dots\}$
integers $\{0, 1, 2,\dots\}$ according to a