Formulas
- Secant method
- Second Hardy–Littlewood conjecture
- Second derivative
- Second fundamental form
- Second law of thermodynamics
- Secure Remote Password protocol
- Secure multi-party computation
- Segment tree
- Segre's theorem
- Sellmeier equation
- Semi-major and semi-minor axes
- Semilinear map
- Separable extension
- Series-parallel partial order
- Set (mathematics)