Formulas
- Ramanujan's sum
- Ramanujan tau function
- Ramsey's theorem
- Ramsey interferometry
- Random geometric graph
- Randomized algorithm
- Range (aeronautics)
- Rapidity
- Rare disaster
- Rarita–Schwinger equation
- Rayleigh's quotient in vibrations analysis
- Reaction–diffusion system
- Real projective line
- Receiver operating characteristic
- Reciprocal polynomial