Let be the group ring of a group over a ring .
Let be an element of . The support of , often written , is the set of elements of which occur with non-zero coefficient in the expansion of .
Thus:
![$ R[G]$](http://images.planetmath.org:8080/cache/objects/5400/l2h/img1.png "$ R[G]$"){kind=small}
![$ R[G]$](http://images.planetmath.org:8080/cache/objects/5400/l2h/img5.png "$ R[G]$"){kind=small}
