> Zero is not a Natural Number because it is not a counting number, and infact > was developed at a later time. (Or so they say.) You don't count to 3 > saying 0, 1, 2, 3.
Zero is a natural number according to some people such as Eric Hehner from the University of Toronto. The following is what he said in one of his books:
"Your life begins at year 0, a highway begins at mile 0, and so on."
If we treat the number zero differently, things can get unnecessarily complicated. For example, if people used the number zero like the way they use other numbers, we wouldn't have something like "unchanged" or "<= =>" in the stock market report.
As I understand, the definition as to whether or not zero is a natural number is not universal. Personally, I consider zero as a natural number.