- rotary dispersion
- rotary expander
- rotary flowmeter
- rotary gap
- rotary selector
- rotary switch
- rotation circulator
- rotational emf
- rotational relaxation
- rotator
- rotofreezer
- rotor plate
- rotten ice
- rough reading
- routing
- routing plan
- Rowland ring
- RPM counter
- ruggedized instrument
- ruhmkorff coil
- Runge vector
- running voltage
- Rutherford backscattering
- saddle-shaped
- safety clearance
- safety system
- rountne maintenance
- runaway speed
- running value
- rupture member
- rural atmosphere
- sabin
- rule
- rutherford
- safe refrigerant
- safety cutout
- safety lamp
- safety thermostat
- room load
- room thermostat
- root locus
- rotary machine
- rotary seal
- rotary solenoid
- rotating field
- rotating machine
- rotation
- rotoflector
- rotor winding
- rototrol
- rough approximation
- Routh conditions
- routine test
- row element
- Rowland current
- ruby
- salient pole
- salinometer
- saltness
- saltwater ice
- saltwater icing
- run cycle
- run motor
- rupture stress
- Rydberg
- saccharimetry
- saddle
- safety switch
- samplier
- sampling chamber
- sampling control
- sampling test
- sanding
- satellite
- satellite communication
- satellite line
- saturable transformer
- saturated absorbent
- saturated brine
- saturated liquid
- saturated refrigerant
- saturated temperature
- saturation
- saturation boundary
- saturation line
- saturation process
- sawdust
- scanning loss
- scatterer
- scattering loss
- Schering bridge
- Schmitt limiter
- sclera
- scleroscope
- sand filter
- sand load
- sandwich
- sandwich structure
- Sargent cycle
- saturated condition