0-forms, 1-forms, 2-forms, etc. are called differential forms.

Fundamental scalar function operations are addition, pointwise product and differentiation. These can be generalized to differential forms.

An example of a solid or surface of a sphere is used to show the relationship between 3-forms and 2-forms.

There are sign changes related to antisymmetry in the derivation rule for differentiation. The differentiation operator is nilpotent, d(dw) = 0.