Rodrigues's Curvature Formula
where
is the unit Normal Vector and 
is one of the two Principal Curvatures.See also Normal Vector, Principal Curvatures- Turán's Theorem
- Tutte Polynomial
- Tutte's Graph
- Tutte's Theorem
- Twin Peaks
- Twin Prime Conjecture
- Twin Primes
- Twin Primes Constant
- Twins
- Twirl
- Twist
- Twisted Chevalley Groups
- Twisted Conic
- Twisted Sphere
- Twist Map
- Twist Move
- Twist Number
- Twist-Spun Knot
- Two
- Two-Ears Theorem
- Two-Point Distance
- Two Triangle Theorem
- Tychonof Compactness Theorem
- Type
- Type I Error