Set Difference
The set difference 
is defined by
The same symbol is also used for Quotient Groups.
- Rectangle Squaring
- Rectangular Coordinates
- Rectangular Distribution
- Rectangular Hyperbola
- Rectangular Parallelepiped
- Rectangular Projection
- Rectifiable Current
- Rectifiable Set
- Rectification
- Rectifying Latitude
- Rectifying Plane
- Recurrence Relation
- Recurrence Sequence
- Recurring Digital Invariant
- Recursion
- Recursive Function
- Recursive Monotone Stable Quadrature
- Red-Black Tree
- Red Net
- Reduced Amicable Pair
- Reduced Fraction
- Reduced Latitude
- Reducible Crossing
- Reducible Matrix
- Reducible Representation