1) The set of all nonnegative integers is usually called the nonnegative integer set (or natural number set). 2) The set of all rational numbers is called rational number set;

3) Positive integers and negative integers are collectively referred to as integers. All real numbers, including 0 (that is, numbers without imaginary parts) are integers. ...-3 -2 - 1 0 1 2 3 ...

Integer set: z = {...-3,-2,-1,0,1,2, 3 ...}