WeylAlgebra -- an option used when creating a polynomial ring
to specify that a Weyl algebra is to be produced.
A Weyl algebra is an algebra in which some of the variables behave
as derivatives with respect to the other variables.
i1 : R = ZZ/101[x,dx,y,dy,WeylAlgebra => {x=>dx, y=>dy}];
The list {x=>dx, y=>dy} indicates that the variable dx
is to play the role of the derivative with respect to x, and
that y is to play the role of the derivative with respect
to y.