radi - real
- radial
- radial displacement error
- radial engine
- radial splitter
- radial strut
- radial-flow compressor
- radial-flow turbine
- radian
- radiation
- radiation field
- radiation field pattern
- radiator exit shutter
- radiator shutter
- radio
- radio (communication) failure
- radio (communication) failure
- radio aids
- radio alert
- radio altimeter
- radio approach aids
- radio band
- radio beacon
- radio beam
- radio bearing
- radio call sign
- radio channel
- radio check
- radio communication
- radio communication equipment
- radio communication station
- radio compass
- radio compass station
- radio contact
- radio control board
- radio detector
- radio deviation
- radio direction finder
- radio direction finding
- radio direction-finding station
- radio directional bearing
