- Shot peening
- Shotcrete
- Shower
- Sickle cell disease
- Siderite
- Sidewalk
- Siding
- Sieves
- Sigma bonds
- Signal processing
- Signal-to-noise ratio
- Silane
- Silanes
- Silanol
- Silica fume
- Silica gel
- Silicate minerals
- Silicates
- Silicene
- Siliceous ooze
- Silicic
- Silicic acid
- Silicides
- Silicification
- Silicon
- Silicon carbide
- Silicon dioxide
- Silicon monoxide
- Silicon nanowires
- Silicon nitride
- Silicon photonics
- Silicon quantum dots
- Silicon tetrachloride
- Silicon tetrafluoride
- Silicon-oxygen bond
- Silicone
- Silicone oil
- Silicone rubber
- Silicosis
- Silk
- Sill plate
- Sills
- Silos
- Siloxane
- Silsesquioxane
- Silt
- Siltation
- Siltstone
- Silver
- Silver chloride electrode
- Silver nanoparticles
- Silver nitrate
- Silver sulfate
- Silver sulfide
- Silylation
- Similitude
- Simulated annealing
- Sine and cosine
- Sine waves
- Single bond
- Single crystals
- Single points of failure
- Single-electron transistor
- Single-molecule magnets
- Single-sideband modulation
- Singlet oxygen
- Sintering
- Siphons
- Skarn
- Skeletal muscle
- Skeleton
- Skin
- Skin effect
- Skywave
- Slag
- Slaking
- Slate
- Sleeve valves
- Slip
- Slip casting
- Slip forming
- Slip ratio
- Slope
- Slope stability
- Sludge
- Slug flow
- Sluice
- Slurry
- Slurry wall
- Small intestine
- Small molecule
- Small satellites
- Smart glass
- Smart materials
- Smartphone
- Smectite
- Smelting
- Smithsonite
- Smog
- Smoke
- Smoke detectors
- Smoke point
- Smokeless fuel
- Snips
- Snow
- Snowboard
- Snowflakes
- Snowmelt
- Soap
- Soap bubbles
- Soda lime
- Soda-lime glass
- Sodalite
- Sodium
- Sodium acetate
- Sodium aluminosilicate
- Sodium amide
- Sodium azide
- Sodium benzoate
- Sodium bicarbonate
- Sodium bismuthate
- Sodium borohydride
- Sodium carbonate
- Sodium channels
- Sodium chlorate
- Sodium dichromate
- Sodium formate
- Sodium gluconate
- Sodium hydroxide
- Sodium hypochlorite
- Sodium laureth sulfate
- Sodium nitrate
- Sodium nitrite
- Sodium oxide
- Sodium perborate
- Sodium peroxide
- Sodium phosphate
- Sodium salicylate
- Sodium selenite
- Sodium silicate
- Sodium sulfate
- Sodium sulfide
- Sodium tetrafluoroborate
- Sodium tetraphenylborate
- Sodium thiosulfate
- Sodium-cooled fast reactor
- Sodium-potassium alloy
- Sodium-potassium pump
- Softening point
- Software testing