- ratio of external division
- ratio of greater inequality
- ratio of internal division
- ratio of magnification
- ratio of progression
- ratio of similitute
- ratio of survival
- ratio paper
- ratio programming
- ratio scale
- ratio set
- ratio test
- Ratner, M.
- RATS sequence (＝“reverse, add, then sort the digits” sequence)
- R-automorphism
- ravine function
- raw
- raw data
- raw estimate
- raw moment
- ray
- ray approximation
- ray class
- ray class field
- ray class group