Arborescence
A Digraph is called an arborescence if, from a given node 
known as the Root, there is exactly oneelementary path from to every other node 
.
- Reef Knot
- Re-Entrant Circuit
- Refinement
- Reflection
- Reflection Property
- Reflection Relation
- Reflexible
- Reflexible Map
- Reflexive Closure
- Reflexive Graph
- Reflexive Reduction
- Reflexive Relation
- Reflexivity
- Region
- Regression
- Regression Coefficient
- Regula Falsi
- Regular Function
- Regular Graph
- Regular Isotopy
- Regular Isotopy Invariant
- Regularity Theorem
- Regularized Beta Function
- Regularized Gamma Function
- Regular Local Ring