- signaling system
- significant condition
- significant frequency
- signum function
- silencer
- silicon crystal
- silicon doping
- silicon FET
- silicon film
- silicon gate
- silicon photocell
- silicon photodiode
- silicon substrate
- silicon wafer
- sinusoidal dispersal
- sinusoidal interference
- sinusoidal oscillation
- sinusoidal voltage
- skew line
- slack
- slant zero
- slave station
- slew
- slewed antenna
- slip ring
- slope
- slot dipole
- slotted system
- smooth earth
- skilled operator
- skin antenna
- skin effect
- skip distance
- skip maneuver
- skirt
- sky phone
- slant polarization
- slave clock
- sleeve antenna
- slewing
- slide
- snapshot dump
- soft key
- soft tube
- software compatible
- software package
- software specification
- slant distance
- slant range
- small computer
- slip
- slot time
- small signal
- smoothing
- soft sector
- soft superconductor
- solar limp
- solar orbit
- solar plate
- solar sensor
- solar space
- solar spot
- solar-ionospheric
- solid curve
- solid line
- solid propellant
- solution
- sort routine
- sorter
- sorting
- sorting machine
- sound articulation
- sound carrier
- sound component
- slant path
- slew rate
- smart phone
- smooth line
- snubber network
- social security
- software maintenance
- software simulator
- solar activity
- solar array
- solar cycle
- solar eclipse
- solar flare
- solar generator
- solar irradiance
- solar sail
- solar storm
- solar-powered
- sound modes
- sound programme
- sound range
- sound reproduction
- sound track
- sounder sequence
- sounding balloon
- sounding signal