Ket
A Contravariant Vector, denoted 
. The ket is Dual to theCovariant Bra 1-Vector 
. Taken together, the Bra andket form an Angle Bracket (bra+ket = bracket) 
. The ket is commonly encountered inquantum mechanics. 
- Discriminant (Quadratic Form)
- Discriminant (Second Derivative Test)
- Disdyakis Dodecahedron
- Disdyakis Triacontahedron
- Disjoint
- Disjunction
- Disjunctive Game
- Disk
- Disk Covering Problem
- Disk Lattice Points
- Dispersion Numbers
- Dispersion Relation
- Dispersion (Sequence)
- Dispersion (Statistics)
- Disphenocingulum
- Disphenoid
- Dissection
- Dissection Puzzles
- Dissipative System
- Distance
- Distinct Prime Factors
- Distribution
- Distribution Function
- Distribution (Functional)
- Distribution Parameter