- Square metre
- Square mile
- Square waves
- Square yard
- Squid
- Stabilizers
- Stable isotope ratio
- Stable nuclide
- Stack effect
- Stacking-fault energy
- Stainless steel
- Stalactites
- Stalagmites
- Stall
- Stamping
- Standard atmosphere
- Standard atomic weight
- Standard electrode potential
- Standard enthalpy of formation
- Standard gravity
- Standard hydrogen electrode
- Standard state
- Standing waves
- Stannite
- Star
- Starch
- Starch gelatinization
- Starter
- State functions
- States of matter
- Static electricity
- Static light scattering
- Static pressure
- Statically indeterminate
- Stationary engine
- Statistical mechanics
- Status register
- Steady state
- Steam
- Steam engines
- Steam explosion
- Steam reforming
- Steam turbines
- Stearic acid
- Steel abrasive
- Steel and tin cans
- Steel casting
- Steel fibre-reinforced shotcrete
- Steel frame
- Steel grades
- Steel mills
- Steel plate shear wall
- Steel wool
- Steelmaking
- Stellar nucleosynthesis
- Stenosis
- Step-growth polymerization
- Stepper motors
- Steradians
- Stereochemistry
- Stereotactic surgery
- Sterilization
- Stern
- Stevens-Johnson Syndrome
- Stibine
- Stibnite
- Stiffness
- Stille reaction
- Stilt
- Stimulant
- Stishovite
- Stochastic
- Stock
- Stockwork
- Stoichiometry
- Stokes shift
- Stokes' law
- Stomach
- Stone carving
- Stone mastic asphalt
- Stone veneer
- Stone walls
- Stone-wales defect
- Stonemasonry
- Stoneware
- Stoping
- Stoppers
- Storage tanks
- Storey
- Storm drains
- Stove
- Strain
- Strain rate
- Strain-rate tensor
- Straits
- Strata
- Stratigraphic section
- Stratigraphy
- Straw
- Straw-bale construction
- Streak
- Stream
- Stream bed
- Strength of materials
- Stress concentration
- Stress corrosion cracking
- Stress intensity factor
- Stress resultants
- Stress-energy tensor
- Stress-strain curve
- Striations
- String theory
- String vibration
- Stringers
- Stroke
- Strontianite
- Strontium
- Strontium carbonate
- Strontium-90
- Structural analysis
- Structural biology
- Structural element
- Structural engineering
- Structural engineers
- Structural formula
- Structural insulated panels
- Structural isomers
- Structural rigidity
- Structural robustness
- Structural steel
- Structural system
- Structure factor
- Struts
- Stucco
- Stud welding
- Sturm-Liouville theory
- Styrene
- Subbase
- Subcritical reactor
- Suberin
- Sublimation
- Submerged arc welding
- Suboxides
- Subsidence
- Substances of very high concern
- Subtraction
- Sucker rod
- Sucrose
- Suction
- Sugar