- self-modulation
- self-quenching
- self-reset
- secondary condenser
- secondary distribution
- secondary emission
- secondary refrigerant
- secondary refrigeration
- secondary winding
- secondary yield
- section insulator
- sectional boiler
- sectional view
- sectionalized busbar
- sector
- secular
- secular aberration
- secular parallax
- secular variation
- security
- sedimentation potential
- seep
- segment diaphragm
- selecting finger
- selection bar
- self-adjoint
- self-capacitance
- self-collision
- self-demagnetization
- self-evaporation
- self-focusing
- self-interference
- self-luminous
- self-powered
- self-reversal
- selsyn drive
- semi-integral
- semiflooded condition
- semiquantitative analysis
- semirigid insulation
- seism behaviour
- selection
- selective adjustment
- selectivity
- self-congruent
- self-consistent
- self-excited
- self-inductance
- self-inductor
- self-ionization
- self-oscillation
- self-radiation
- self-reacting
- self-shielding
- self-sustaining
- semi-insulating
- semihermetic construction
- semimetals
- semipure
- sending station
- sensibility
- sensitive switch
- sensitive volume
- sensitivity
- sensitization
- sensor
- sentinel
- separate cooling
- separate excitation
- separated component
- separately excited
- separation factor
- septet
- septivalence
- sequential control
- series capacitor
- series compensation
- seismometry
- seizure signal
- select
- selective cooling
- selective scattering
- selector switch
- self-absorption
- self-activated
- self-contained
- self-cooled
- self-defocusing
- self-evaporating
- self-exciting
- self-fields
- self-impedance
- self-maintaining
- self-moving
- self-progarating
- self-refrigeration
- self-shadowing
- self-stabilizing
- self-starting
- self-ventilation