- optical receiver
- optical recognition
- optical recording
- optical rectifier
- optical reflectometer
- optical refraction
- optical relay
- optical repeater
- optical resist
- optical resonance
- optical resonator
- optical sag
- optical scale
- optical scanner
- optical scanning
- optical sensing
- optical sensor
- optical servo
- optical sight
- optical signal
- optical sound
- optical source
- optical spectrograph
- optical spectrum
- optical splice
- optical square
- optical stepper
- optical storage
- optical surface
- optical switching
- optical system
- optical tape
- optical telescope
- optical theodolite
- optical thickness
- optical tool
- optical track
- optical transition
- optical transmission
- optical transmitter
- optical tuning
- optical videodisk
- optical wave
- optical waveguide
- optical wavelength
- optical window
- opticalaxial angle
- optically
- optically empty
- optically-flat
- opticator
- optician
- opticist
- opticity
- optics
- optimal
- optimal conditions
- optimal control
- optimal humidity
- optimal path
- optimal program
- optimal programming
- optimal recalculation
- optimal reliability
- optimal route
- optimal sampling
- optimal scale
- optimal smoother
- optimal solution
- optimal strategy
- optimal system
- optimal trajectory
- optimal value
- optimality
- optimality criterion
- optimality principle
- optimate
- optime
- optimism
- optimist
- optimistic
- optimistically
- optimization
- optimization control
- optimize
- optimized code
- optimizer
- optimum
- optimum allocation
- optimum bunching
- optimum burnup
- optimum capacity
- optimum catch
- optimum code
- optimum conditions
- optimum coupling
- optimum cure
- optimum damping
- optimum density
- optimum filter