Definition:Positive/Number

Definition
The concept of positive can be applied to the following sets of numbers:
 * $(1): \quad$ The integers $\Z$
 * $(2): \quad$ The rational numbers $\Q$
 * $(3): \quad$ The real numbers $\R$

The complex numbers cannot be ordered, so there is no such concept as a positive complex number.

As for the natural numbers, they are all positive by dint of their being the non-negative integers.