The reason why Z stands for integer set is because it involves the contribution of a German female mathematician named Nott to ring theory.
In 1920, she introduced the concepts of "left module" and "right module". The ideal theory of the whole ring written in 192 1 is a milestone in the development of commutative algebra. Because she is German, the integer in German is called Zahlen, so she recorded the integer ring as Z at that time, and the integer set has been represented by Z since then.
Several commonly used symbols in mathematics can be used directly without explanation: n stands for natural number set, z stands for integer set, q stands for rational number set, r stands for real number set, and c stands for complex number set.
N stands for the set of natural numbers in the set. A non-negative integer set is a specific set, which refers to the set of all natural numbers, and is commonly represented by the symbol n. Non-negative integers include positive integers and zeros.