HOMOMORPHISM / HOMOMORPHISMS
A homomorphism is a mapping between two algebraic systems of the same type1 (one source mentions only monoids2 while another mentions groups, rings or vectors3) such that:
(Also see structures.)
1 McGraw-Hill dictionary of Physics and Mathematics, 1978, p. 458.
2 Michael A. Arbib, A. J. Kfoury and Robert N. Moll, A Basis for Theoretical Computer Science (New York: Springer-Verlag, 1981), p. 47.