Girth
The length of the shortest Cycle in a Graph.
| Girth | Example |
| 3 | Tetrahedron |
| 4 | Cube,  |
| 5 | Petersen Graph |
- Thomson Lamp Paradox
- Thomson Problem
- Thomson's Principle
- Thousand
- Three
- Three-Colorable
- Threefoil Knot
- Three-In-A-Row
- Three Jug Problem
- Three-Valued Logic
- Thue Constant
- Thue-Morse Constant
- Thue-Morse Sequence
- Thue Sequence
- Thue-Siegel-Roth Theorem
- Thue-Siegel-Schneider-Roth Theorem
- Thue's Theorem
- Thurston's Geometrization Conjecture
- Thwaites Conjecture
- Ticktacktoe
- Tic-Tac-Toe
- Tight Closure
- Tightly Embedded
- Tiling
- Tiling Theorem