S

S may refer to:
*S function, a function by Chris Bird
*Three maps by Fish:
**S map
**SS map
**S(n) map
*Frantic frog function S(n) or FF(n), the maximal finite number of steps that a Turing machine can make before halting, invoking at most n states
*The S(n) = n+1
*A structure in BEAF.