- sampled data control system
- sand mill
- sand-bed filter
- saturation
- Sauter mean diameter
- scale factor
- scale up
- scale, fouling
- scaled particle theory
- scaling
- scheduling of production
- Schmidt number
- scraper
- screen analysis
- screw mixer
- screw pump
- secant method
- second law of thermodynamics
- second virial coefficient
- second-order phase transition
- secondary metabolism
- secondary reaction
- sedigraph
- sediment
- sedimentation centrifuge
- sedimentation, settling
- sedimentometer
- seed crystal
- segment
- segregation
- selective control
- selectivity
- selectivity coefficient
- semi-continuous culture
- semi-continuous process
- semi-empirical model
- semi-ideal solution
- semipermeable membrane
- sensitivity analysis
- separation efficiency
- separation factor
- separation sequence
- separation sharpness
- sequential design
- sequential modular approach
- sequential significance test
- serial correlation
- serum-free culture
- settled layer
- shaft work