Bra
A (Covariant) 1-Vector denoted 
. The bra is Dual to the Contravariant Ket, denoted 
. Taken together,the bra and Ket form an Angle Bracket (bra+ket = bracket). The bra is commonly encountered inquantum mechanics. 
- Unit Step
- Unit Vector
- Unity
- Univalent Function
- Univariate Function
- Univariate Polynomial
- Universal Graph
- Universal Statement
- Universal Turing Machine
- Unknot
- Unknotting Number
- Unless
- Unlesss
- Unmixed
- Unpoke Move
- Unsafe
- Unsolved Problem
- Unstable Improper Node
- Unstable Node
- Unstable Spiral Point
- Unstable Star
- Untouchable Number
- U-Number
- Upper Bound
- Upper Integral