olemus
rühm, mille binaartehe on kommutatiivne, st a · b = b · a iga a ja b korral
= a group whose binary operation is commutative

ülevaateid
http://mathworld.wolfram.com/AbelianGroup.html
https://www.encyclopediaofmath.org/index.php/Abelian_group
https://en.wikipedia.org/wiki/Abelian_group
https://en.wikipedia.org/wiki/Free_abelian_group
https://sites.pitt.edu/~gmc/algebra/chapter2.pdf