In algebra, a filtered ring A is said to be almost commutative if the associated graded ring is commutative. Basic examples of almost commutative rings involve differential operators. For example, the enveloping algebra of a complex Lie algebra is almost commutative by the PBW theorem. Similarly, a Weyl algebra is almost commutative. See also Ore condition Gelfand–Kirillov dimension References Victor Ginzburg, Lectures on D-modules Ring theory