A set of numbers is simply a set of numbers, and a group of numbers are combined together.

Some commonly used number sets in mathematics and their representations;

The set of all positive integers is called positive integer set, which is denoted as N*, Z+ or n+;

The set composed of all nonnegative integers is called nonnegative integer set (or natural number set), and is denoted as n;

The set composed of all integers is called integer set, which is denoted as z;

The set of all rational numbers is called rational number set, and it is recorded as q;

The set composed of all real numbers is called real number set, which is denoted as r;

The set composed of all imaginary numbers is called imaginary number set, which is denoted as I;

The set of complex numbers composed of all real numbers and imaginary numbers is called complex number set, and it is recorded as C.