Abelian.

1. Abelian Group (also other commutative algebraic structures, and related structures like Abelian extensions)
2. Abelian theorem
3. Abelian Variety (as well as surface)
4. Abelian function
5. Abelian integral
6. Abelian Category
7. Abelian equation (used in web geometry, also appears as Abelian relation)