- Soil acidification
- Soil aggregate stability
- Soil biology
- Soil carbon
- Soil compaction
- Soil conditioners
- Soil consolidation
- Soil contamination
- Soil gas
- Soil mechanics
- Soil pH
- Soil resistivity
- Soil science
- Soil structure
- Sol-gel process
- Solar air conditioning
- Solar cells
- Solar chimney
- Solar constant
- Solar cookers
- Solar energy
- Solar gain
- Solar mass
- Solar neutrinos
- Solar panels
- Solar thermal collector
- Solar-cell efficiency
- Solder
- Solderability
- Soldering
- Solenoids
- Solid acid
- Solid fuel
- Solid hydrogen
- Solid mechanics
- Solid nitrogen
- Solid oxygen
- Solid rocket boosters
- Solid solution
- Solid solution strengthening
- Solid-propellant rocket
- Solid-state chemistry
- Solid-state electronics
- Solid-state physics
- Solitons
- Solubility
- Solubility equilibrium
- Solvated electron
- Solvation
- Solvatochromism
- Solvay process
- Solvent effects
- Solvents
- Somatosensory system
- Somatostatin
- Somnolence
- Sonic booms
- Soot
- Sorbents
- Sorbic acid
- Sorel cement
- Sound
- Sound intensity
- Sound level meter
- Sound power
- Sound pressure
- Soundproofing
- Source reduction
- Soybean oil
- Space debris
- Space frame
- Space groups
- Space station
- Space sustainability
- Space weather
- Space-based solar power
- Spacetime
- Spall
- Spallation
- Span
- Spark
- Spark plugs
- Spars
- Spatial scale
- Special relativity
- Specific energy
- Specific heat capacity
- Specific modulus
- Specific speed
- Specific strength
- Specific surface area
- Specific volume
- Specific weight
- Specified minimum yield strength
- Spectral density
- Spectrophotometry
- Spectroscopy
- Specular reflection
- Speed of light
- Speed of sound
- Speleothems
- Spent fuel pool
- Spent nuclear fuel
- Sperm
- Sphalerite
- Sphere
- Sphericity
- Spherometer
- Spherulites
- Sphygmomanometer
- Spiegeleisen
- Spillways
- Spin
- Spin casting
- Spin echo
- Spin hall effect
- Spin ice
- Spin magnetic moment
- Spin polarization
- Spin quantum number
- Spin waves
- Spin-lattice relaxation
- Spin-orbit interaction
- Spin-spin relaxation
- Spin-transfer torque
- Spinal cord
- Spindle oil
- Spinel
- Spinning
- Spintronics
- Splat quenching
- Spleen
- Spodumene
- Spoilers
- Spontaneous combustion
- Spontaneous fission
- Spontaneous magnetization
- Spontaneous process
- Sporosarcina pasteurii
- Spot
- Spot welding
- Spray foam
- Spray forming
- Spring steel
- Springs
- Sputter deposition
- Sputtering
- Square antiprism
- Square inches
- Square kilometre