Compact Space
A Topological Space is compact if every open cover of 
has a finite subcover. In other words, if is theunion of a family of open sets, there is a finite subfamily whose union is . A subset 
of a TopologicalSpace is compact if it is compact as a Topological Space with the relative topology (i.e., every family ofopen sets of whose union contains has a finite subfamily whose union contains ).
- Banach-Hausdorff-Tarski Paradox
- Banach Measure
- Banach Space
- Banach-Steinhaus Theorem
- Banach-Tarski Paradox
- Bang's Theorem
- Bankoff Circle
- Banzhaf Power Index
- Barber Paradox
- Barbier's Theorem
- Bare Angle Center
- Bar (Edge)
- Barnes G-Function
- Barnes' Lemma
- Barnes-Wall Lattice
- Barnsley's Fern
- Bar Polyhex
- Bar Polyiamond
- Barrier
- Barth Decic
- Barth Sextic
- Bartlett Function
- Barycentric Coordinates
- Baseball
- Baseball Cover