 More general conditions which guarantee commutativity of a ring are also known.A graded ring "R" = ⨁"i"∊Z "R""i" is called graded-commutative if
If the "R""i" are connected by differentials ∂ such that an abstract form of the product rule holds, i.e.,
"R" is called a commutative differential graded algebra (cdga).An example is the complex of differential forms on a manifold, with the multiplication given by the exterior product, is a cdga.