Mathematical Left Double Angle Bracket

Mathematical Left Double Angle Bracket at U+27EA opens a paired mathematical delimiter shaped like a doubled angle bracket. It belongs to the Miscellaneous Mathematical Symbols-A block and is used when ordinary parentheses, brackets, or single angle brackets are not visually or semantically specific enough. In mathematics and theoretical computer science, it most often appears with its matching right delimiter to enclose objects that need a special bracket convention. Authors use pairs such as ⟪x, y⟫ for selected inner products, semantic interpretations, ordered structures, or syntactic forms when other bracket styles are already assigned meanings in the same work. It is also seen in formal logic, denotational semantics, and programming-language theory, where double brackets commonly mark “the meaning of” an expression, as in enclosing a term to denote its interpretation in a model. The exact reading is set by the author’s notation, so it should be understood as a left double angle bracket rather than as a universal operator with one fixed mathematical value.