- Sanitary sewer
- Saponification
- Sapphire
- Saprolite
- Satellite internet constellation
- Satellites
- Saturated-surface-dry
- Saturation
- Saturation diving
- Saybolt Universal Viscosity
- Scaffolding
- Scale height
- Scale of temperature
- Scalpel
- Scandium
- Scatter plot
- Scattering
- Scavengers
- Schist
- Schottky diode
- Scintillation
- Scintillation counters
- Scintillators
- Scissors
- Scram
- Scrap
- Scratch hardness
- Scree
- Screed
- Screw piles
- Screw pumps
- Screw thread
- Screws
- Scroll compressor
- Scrubber
- Sea ice
- Sea level
- Sea salt
- Seafloor spreading
- Sealant
- Season cracking
- Seasonal thermal energy storage
- Seawalls
- Seawater
- Second industrial revolution
- Second law of thermodynamics
- Second moment of area
- Secretion
- Sedatives
- Sediment
- Sediment control
- Sediment transport
- Sedimentary rock
- Sedimentary structures
- Sedimentation
- Sedimentology
- Seebeck coefficient
- Seed crystals
- Segregation in concrete
- Seismic analysis
- Seismic code
- Seismic loading
- Seismology
- Seizures
- Selection rules
- Selenate
- Selenides
- Selenite
- Selenium
- Selenium dioxide
- Self-assembly
- Self-cleaning glass
- Self-cleaning surfaces
- Self-consolidating concrete
- Self-healing material
- Self-ionization of water
- Semi-automatic transmission
- Semi-major and semi-minor axes
- Semi-monocoque
- Semi-trailer
- Semi-trailer truck
- Semiconductor detector
- Semiconductor device fabrication
- Semiconductor devices
- Semiconductor packages
- Semiconductors
- Semimetals
- Semipermeable membrane
- Sense of smell
- Sensible heat
- Sensitivity and specificity
- Sensor fusion
- Sensors
- Separation processes
- Separatory funnel
- Sepsis
- Septic tank
- Septum
- Serotonin transporter
- Serpentinite
- Server farms
- Serviceability
- Sesquioxides
- Sessile drop technique
- Sewage
- Sewage sludge
- Sewage treatment
- Sexagesimal
- Sexually transmitted infections
- Shaders
- Shale
- Shallow foundation
- Shampoo
- Shape optimization
- Shape-memory alloys
- Shape-memory polymers
- Shared space
- Shared-use paths
- Sharp sand
- Shear band
- Shear flow
- Shear force
- Shear modulus
- Shear rate
- Shear strength
- Shear stress
- Shear thinning
- Shear velocity
- Shear walls
- Shearing
- Sheet metal
- Sheet resistance
- Shell-and-tube heat exchanger
- Shellac
- Shells
- Shewanella oneidensis
- Shielding effect
- Shielding gas
- Shims
- Shipping containers
- Ships
- Shock
- Shock absorbers
- Shock waves
- Shoelace formula
- Short circuit
- Short ton
- Short-path distillation
- Shortite
- Shortness of breath