Closure
A Set 
and a Binary Operator 
are said to exhibit closure if applyingthe Binary Operator to two elements returns a value which is itself a member of .
The term ``closure'' is also used to refer to a ``closed'' version of a given set. The closure of a Set can be definedin several equivalent ways, including
- 1. The Set plus its Limit Points, also called ``boundary'' points, the union ofwhich is also called the ``frontier,''
- 2. The unique smallest Closed Set containing the given Set,
- 3. The Complement of the interior of the Complement of the set,
- 4. The collection of all points such that every Neighborhood of them intersects the original Set in anonempty Set.
is itself.See also Binary Operator, Existential Closure, Reflexive Closure, Tight Closure, Transitive Closure- Rhombic Icosahedron
- Rhombicosacron
- Rhombicosahedron
- Rhombicosidodecahedron
- Rhombic Polyhedron
- Rhombic Triacontahedron
- Rhombicuboctahedron
- Rhombidodecadodecahedron
- Rhombihexacron
- Rhombihexahedron
- Rhombitruncated Cuboctahedron
- Rhombitruncated Icosidodecahedron
- Rhombohedron
- Rhomboid
- Rhomboidal Dodecahedron
- Rhombus
- Rhumb Line
- Ribbon Knot
- Ribet's Theorem
- Riccati-Bessel Functions
- Riccati Differential Equation
- Ricci Curvature
- Ricci Tensor
- Rice Distribution
- Richardson Extrapolation