- real sequence
- real series
- real solution
- real space
- real spectral measure
- real spectrum
- real sphere
- real statement
- real structure
- real subalgebra
- real submanifold
- real surface
- real symmetric kernel
- real system
- real theory
- real time
- real-time algorithm
- real-time computation
- confocal conics
- confocal coordinate
- confocal curves
- confocal ellipses
- confocal ellipsidal coordinate
- confocal ellipsoids
- confocal family