Let be a graded ring. An ideal
is homogenous (also called graded) if for every element
, its homogenous components also belong to
.
An ideal in a graded ring is homogenous if and only if it is a graded submodule. The intersections of a homogenous ideal with the
are called the homogenous parts of
. A homogenous ideal
is the direct sum of its homogenous parts, that is,