Z stands for integer set in mathematics. An integer set is a set of all integers. It includes all positive integers, all negative integers and zeros. In mathematics, integer sets are usually represented by z. German female mathematician's contribution to ring theory, her name is Nott. 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. Among them, when Nott introduced the concept of integer ring (integer set itself is also a number ring), she was German, and the integer in German was called Zahlen, so she wrote the integer ring, and the integer set was used to represent it from then on.