- Saccades
- Saccharin
- Saccharomyces boulardii
- Saccule
- Sacral
- Sacral nerve stimulation
- Sacrifice zones
- Sacrificial anodes
- Sacrificial metal
- Sacroiliac joint
- Sacrospinous ligament
- Sacrotuberous ligament
- Saddle
- Saddle joint
- Saddle points
- Saddle-node bifurcation
- Safe operating area
- Safe-life
- Safe-life design
- Safety barriers
- Safety culture
- Safety engineer
- Safety engineering
- Safety factor
- Safety glass
- Safety instrumented system
- Safety lamp
- Safety life cycle
- Safety pharmacology
- Safety pins
- Safety valve
- Safety-critical
- Safety-critical systems
- Safflorite
- Saffron
- Safranal
- Safranin
- Sag
- Saga GIS
- SageMath
- Sagitta
- Sagittal
- Sagittal plane
- Sagittal suture
- Sagnac effect
- Saidi
- Sails
- Saint-Venant's principle
- Sal ammoniac
- Salen ligands