radi - rece
- radian
- radii
- radio button
- radiosity
- radius
- radius of curvature
- radix
- radix complement
- radix notation
- radix two computer
- radix two counter
- radix-minus-one complement
- ragged array
- ragged text
- raid
- raid tape-array
- raised floor
- raising to a power
- ram
- ram disk
- ramifications
- ramp function
- random
- random access
- random access memory
- random accessing
- random action
- random arrivals
- random changes
- random clock
- random component
- random coupling
- random cross- channel
- random departures
- random dependence
- random distribution
- random element
- random error
- random event
- random factor
