bra-ket

noun

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).

Ask AI about this wordChatGPTClaudePerplexityGoogle AIGrok

Meanings

nounbra-ket (plural bra-kets)

plural bra-kets

  1. natural sciencesThe 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).

Origin

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

Full word history & related roots →
Cite this entry
APA

bra-ket. (n.d.). In WatkinsX Dictionary. Retrieved November 4, 2026, from https://dictionary.watkinsx.com/word/bra-ket

MLA

“bra-ket.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/bra-ket. Accessed November 4, 2026.

Chicago

WatkinsX Dictionary, s.v. “bra-ket,” accessed November 4, 2026, https://dictionary.watkinsx.com/word/bra-ket.

Source: bra-ket on Wiktionary, CC BY-SA 4.0.