Things often have relations

Algebraic structures

Group theory

Ring theory

wayback.archive-it.org/3671/20150528171650/https://www.extension.harvard.edu/open-learning-initiative/abstract-algebra

See Wiki and CosmosBrain, Algebraic structure

Group theory

http://math.stackexchange.com/questions/105285/the-most-common-theorems-taught-in-abstract-algebra

sometimes just called Algebra