The question, "Is zero a natural number?" is more ambiguous than you think. Back when I was in grad school we informally polled the mathematicians in the depar

The question, "Is zero a natural number?" is more ambiguous than you think. Back when I was in grad school we informally polled the mathematicians in the department on whether 0 should be a natural number, and got about an even split. The key factor being what area of math you specialized in. So, for example, people studying logic and combinatorics thought it should be because the empty set comes up a lot. But people studying number theory and combinatorics thought it shouldn't because they are always dealing with things enumerated and starting at 1. When I went through school, I was expected to memorize that natural numbers start with 1, and distinguished them from whole numbers that include 0. But this is an entirely arbitrary distinction. As https://en.wikipedia.org/wiki/Natural_number https://en.wikipedia.org/wiki/Natural_number says, there is no general consensus on whether 0 should be included, and there are a variety of unambiguous terminologies that are preferred for cases where it matters.