Tiling Theorem
Due to Lebesgue and Brouwer. If an 
-D figure is covered in any way by sufficiently small subregions, then there willexist points which belong to at least 
of these subareas. Moreover, it is always possible to find a covering byarbitrarily small regions for which no point will belong to more than regions.
- Truncated Tetrahedral Number
- Truncated Tetrahedron
- Truncation
- Truth Table
- Tschebyshev
- Tschirnhausen Cubic
- Tschirnhausen Cubic Caustic
- Tschirnhausen Cubic Pedal Curve
- Tschirnhausen Transformation
- Tubular Neighborhood
- Tucker Circles
- Tukey's Biweight
- Tukey's Trimean
- Tunnel Number
- Turbine
- Turing Machine
- Turning Angle
- Turán Graph
- Turán's Inequalities
- Turán's Theorem
- Tutte Polynomial
- Tutte's Graph
- Tutte's Theorem
- Twin Peaks
- Twin Prime Conjecture