  Discrete flavor symmetry is explored for an intrinsic property of mass matrix
forms of quarks and leptons. In this paper we investigate the S3 permutation
symmetry and derive the general forms of mass matrices in various types of S3
theories. We also exhibit particular realizations of previous ansatze of mass
matrices, which have often been applied in the literature to the standard model
Yukawa sector. Discrete flavor symmetry is also advantageous for vanishing
matrix elements being dynamically generated in the vacuum of scalar potential.
This is due to the fact that group operations are discrete. While zero elements
themselves do not explain mass hierarchies, we introduce an abelian flavor
symmetry. A non-trivial issue is whether successful quantum numbers can be
assigned so that they are compatible with other (non-abelian) flavor
symmetries. We show typical examples of charge assignments which not only
produce hierarchical orders of mass eigenvalues but also prohibit
non-renormalizable operators which disturb the hierarchies in first-order
estimation. As an explicit application, a flavor model is constructed in grand
unification scheme with S3 and U(1) (or Z_N) flavor symmetries.
