Natural numbers are the nonnegative integers {0, 1, 2, 3,...}, according to most modern mathematics and logic textbooks. Older books sometimes exclude zero, as there is a long history of people thinking that zero is unnatural or not really a number.
Natural numbers are the nonnegative integers {0, 1, 2, 3,...}, according to most modern mathematics and logic textbooks. Older books sometimes exclude zero, as there is a long history of people thinking that zero is unnatural or not really a number.