Natural numbers begin from 0 or 1?... now according to modern maths do we consider set of positive integers as natural numbers {0,1,2...}?
""Some definitions, including the standard ISO 80000-2,^{[1]} begin the natural numbers with 0, corresponding to the non-negative integers0, 1, 2, 3, …, whereas others start with 1, corresponding to the positive integers 1, 2, 3, ….^{[2]}^{[3]}^{[4]}^{[5]} Texts that exclude zero from the natural numbers sometimes refer to the natural numbers together with zero as the whole numbers, but in other writings, that term is used instead for the integers (including negative integers).""(SOURCE:WIKIPEDIA)