Sheffer function

Summary

A Sheffer function on a finite set $A$ is a single operation on $A$ that is functionally complete by itself. Every operation on $A$ can then be written as a composition of copies of it. On $\set{0, 1}$ the binary Sheffer functions are NAND and NOR. Sheffer functions show that one well-chosen operation can carry the whole expressive power of a many-valued logic.