In abbreviations, S. stands for societas, society, or socius, fellow; as F.R.S. fellow of the Royal Society. In medical prescriptions, S.A. signifies secundem artem, according to the rules of art.
In the notes of the ancients, S. stands for Sextus; SP. for Spurius; S.C. for senatus consultum; S.P.Q.R. for senatus populusque Romanus; S.S.S. for stratum super stratum, one layer above another alternately; S.V.B.E.E.Q.V. for sivales, bene est, ego quoque valeo.
As a numeral, S. denoted seven. In the Italian music, S. signifies solo. In books of navigation and in common usage, S. stands for south; S.E. for south-east; S.W. for south-west; S.S.E. for south south-east; S.S.W. for south south-west, _c.