Square Matrix
A Matrix for which horizontal and vertical dimensions are the same (i.e.,an 
Matrix).
- Reidemeister Moves
- Reidemeister's Theorem
- Reinhardt Domain
- Relation
- Relative Error
- Relative Extremum
- Relatively Prime
- Relative Maximum
- Relative Minimum
- Relaxation Methods
- Remainder
- Remainder Theorem
- Rembs' Surfaces
- Removable Crossing
- Removable Singularity
- Rencontres Number
- Rendezvous Values
- Repartition
- Repdigit
- Repeating Decimal
- Repfigit Number
- Replicate
- Representation
- Reptend Prime
- Rep-Tile