In mathematics, S-function may refer to:
- sigmoid function
- Schur polynomials
- A function in the Laplace transformed 's-domain'
In computer science,
- It may be member of a series of graph parameters, see Treewidth § Hadwiger number and S-functions
In physics, it may refer to:
- action functional
In MATLAB, it may refer to:
- A type of dynamically linked subroutine for Simulink.