- Sulfamic acid
- Sulfate minerals
- Sulfidation
- Sulfide minerals
- Sulfide stress cracking
- Sulfite
- Sulfonates
- Sulfur cycle
- Sulfur dioxide
- Sulfur hexafluoride
- Sulfur oxide
- Sulfur trioxide
- Sulfuric acid
- Sulfuryl chloride
- Sun
- Sun-synchronous orbits
- Sunburn
- Sunlight
- Sunscreen
- Super-resolution imaging
- Superabsorbent polymer
- Superacids
- Superalloys
- Supercapacitors
- Supercomputers
- Superconducting magnets
- Superconducting wire
- Superconductivity
- Supercontinents
- Supercooling
- Supercritical airfoil
- Supercritical carbon dioxide
- Supercritical drying
- Supercritical fluid
- Supercritical water oxidation
- Superfluidity
- Supergene
- Superheavy elements
- Superhydrophobic coating
- Superior temporal gyrus
- Superlubricity
- Superoxide
- Superplasticity
- Superplasticizer
- Superposition principle
- Supersaturation
- Supersonic aircraft
- Supersonic speed
- Suprachiasmatic nucleus
- Supramolecular polymers
- Surface area
- Surface energy
- Surface engineering
- Surface finish
- Surface finishing
- Surface modification
- Surface plate
- Surface reconstruction
- Surface roughness
- Surface runoff
- Surface states
- Surface stress
- Surface tension
- Surface water
- Surface waves
- Surfactants
- Surgery
- Surgical instruments
- Surgical suture
- Surveying
- Susceptance
- Suspension
- Sustainable architecture
- Sustainable design
- Sustainable development
- Sustainable engineering
- Sustainable transport
- Swaging
- Swarf
- Swashplate
- Swept wing
- Swimming pool reactor
- Switch
- Switchgear
- Syenite
- Syenogranite
- Sylvite
- Symmetric matrix
- Symmetry
- Synapses
- Synaptic plasticity
- Synaptic vesicles
- Synechococcus elongatus
- Syneresis
- Synergy
- Syngas
- Syntactic foam
- Synthetic biology
- Synthetic fibers
- Synthetic fuel
- Synthetic membranes
- Synthetic rubber
- Syphilis
- Syringes
- Syrup
- System of equations
- System on a chip
- System requirements
- Systems theory
- TBM
- TDP
- TDS
- TIM
- TPMS
- Tabby concrete
- Tablet
- Tablet computers
- Tableware
- Tachycardia
- Taconite
- Tacticity
- Tail rotor
- Tailings
- Tailless aircraft
- Takeoff
- Talc
- Talc carbonate
- Tangent modulus
- Tanks
- Tannic acid
- Tanning
- Tantalite
- Tantalum
- Tantalum pentoxide
- Tap water
- Tar
- Tartaric acid
- Taxiways
- Tear resistance
- Technetium
- Tectonic
- Telegraphy
- Telephone
- Telluride
- Tellurium
- Telomeres
- Temper
- Temperature coefficient
- Temperature gradient
- Temperature measurement