- reflectorscope
- reflex mirror
- refractive power
- regular emission
- regular sequence
- removable back
- repel
- relative aperture
- relative key
- relative loudness
- relativistic theory
- relaxation
- relieve stress
- replanisher
- reprocessing
- reproducing characteristic
- reproducing loss
- reproduction
- repulsion
- repulsive
- repulsive energy
- rerecording
- research reactor
- reservoir
- residual
- resistance
- resistance welding
- resistive
- resistivity
- resistor
- resonance capture
- resonance line
- resonance spectrum
- resonance vibration
- resonant cavity
- response
- restitution
- restoring force
- restraining bath
- resultant
- retarded potential
- retarding torque
- resisting torque
- resonance
- rest
- restart phase
- restoring torque
- resultant moment
- retentivity
- reversal finder
- reverberation time
- reversal film
- reversible
- reversible shutdown
- reversing bath
- reversing ring
- rewind cam
- Reynolds stress
- rider
- rifle grip
- right-hand
- reverse printing
- reversion
- revolving back
- rewind handle
- rheological properties
- rib
- ribbon burner
- ripening
- rise time
- retractable filter
- reverberation room
- residual magnetization
- residual silver
- resonant
- resonate
- resonator
- reticulation
- retort clamp
- retort stand
- retouch
- ring collider
- ring core
- ring flash
- reversal processing
- reverse
- reverser
- revolving diaphragm
- rigid leg
- road resistance
- rod
- rod linkage
- rod system
- roentgen
- Roentgen optics
- roentgenogram
- roll film
- roller lever
- rolling moment
- rolled alloy