- RM-code
- R-method
- R-module
- RMS (= root-mean-square)
- road
- road coloring problem
- Robbins algebra
- Robbins axiom
- Robbins conjecture
- Robbins constant
- Robbins, H.
- Robbins number
- Robert circle
- Robert (of Chester)
- Roberts
- Roberts, J.H.
- Robertson condition
- Robertson conjecture
- Robertson graph
- Robertson, H.P.
- Robertson-Walker metric
- Roberval curve
- Roberval, G.P.
- Robin boundary condition
- Robin constant