Relation
A relation is any Subset of a Cartesian Product. For instance, a Subset of 
, called a(binary) ``relation from 
to 
,'' is a collection of Ordered Pairs 
with firstcomponents from and second components from , and, in particular, a Subset of 
is called a``relation on .'' For a binary relation 
, one often writes 
to mean that is in .
- Trapezium
- Trapezohedron
- Trapezoid
- Trapezoidal Hexecontahedron
- Trapezoidal Icositetrahedron
- Trapezoidal Rule
- Traveling Salesman Constants
- Traveling Salesman Problem
- Trawler Problem
- Trebly Magic Square
- Tredecillion
- Tree
- Tree-Planting Problem
- Tree Searching
- Trefoil Curve
- Trefoil Knot
- Trench Diggers' Constant
- Triabolo
- Triacontagon
- Triacontahedron
- Triad
- Triakis Icosahedron
- Triakis Octahedron
- Triakis Tetrahedron
- Trial