An ideal of a ring is called principal if there is an element of such that

In other words, the ideal is generated by the element . For example, the ideals of the ring of integers are all principal, and in fact all ideals of are principal.

An ideal of a ring is called principal if there is an element of such that

In other words, the ideal is generated by the element . For example, the ideals of the ring of integers are all principal, and in fact all ideals of are principal.

Weisstein, Eric W. "Principal Ideal."
From *MathWorld*--A Wolfram Web Resource. https://mathworld.wolfram.com/PrincipalIdeal.html