Ket

A Contravariant Vector, denoted $\left\vert\psi\right\rangle$. The ket is Dual to the Covariant Bra 1-Vector $\left\langle\psi\right\vert$. Taken together, the Bra and ket form an Angle Bracket (bra+ket = bracket) $\left\langle{\psi\vert\psi}\right\rangle{}$. The ket is commonly encountered in quantum mechanics.

See also Angle Bracket, Bra, Bracket Product, Contravariant Vector, Covariant Vector, Differential k-Form, One-Form