A set is lightface if it is the complement of a set.

The complement of a set A is then given by that portion of the rectangle outside of As circle.

The next proposition, which is also self-dual, says that the complement of a set is the only set that satisfies the complement laws.

The regular elements t are themselves explicitly given as the complement of a set in T, determined by the adjoint action of G, and making up a union of subtori.

The axiom of induction in KP is stronger than the usual axiom of regularity (which amounts to applying induction to the complement of a set (the class of all sets not in the given set)).