bra-ket

Etymology
Concatenation of the terms and, which were introduced in 1939 and in turn derive from the splitting of the English word.

Noun

 * 1)  The scalar product of two vectors (and optionally an operator), in Hilbert space, where the left (row) vector is a bra and the right (column) vector is a ket. Symbolised by ⟨...|...⟩ (bra and ket only) or ⟨...|...|...⟩ (bra, operator, ket).