In mathematics, the ideal class group (or class group) of an algebraic number field K {\displaystyle K} is the quotient group J K / P K {\displaystyle J_{K}/P_{K}} where J K {\displaystyle J_{K}} is the group of fractional ideals of the ring of integers of K {\displaystyle K} , and P K {\displaystyle P_{K}} is its subgroup of principal ideals. The class group is a measure of the extent to which unique factorization fails in the ring of integers of K {\displaystyle K} .
In mathematics, the ideal class group (or class group) of an algebraic number field K {\displaystyle K} is the quotient group J K / P K {\displaystyle J_{K}/P_{K}} where J K {\displaystyle J_{K}} is the group of fractional ideals of the ring of integers of K {\displaystyle K} , and P K {\displaystyle P_{K}} is its subgroup of principal ideals. The class group is a measure of the extent to which unique factorization fails in the ring of integers of K {\displaystyle K} .
Source: Wikipedia "Ideal class group" · CC BY-SA 4.0
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