U+27F8 "⟸" Long Leftwards Double Arrow Unicode Character

U+27F8 "⟸" Long Leftwards Double Arrow is a mathematical symbol that represents a double line arrow pointing to the left, typically used in formal logic, set theory, and linear algebra to denote biconditional relationships, logical equivalence, or a reverse mapping between sets. It is part of the Supplemental Arrows-A block and is distinct from its more common single-line counterpart by its thicker, double-stroked design, which often indicates a stronger or bidirectional implication when combined with its rightward counterpart. In many technical contexts, this character serves as a visual placeholder for the phrase "if and only if," though it lacks a universally standardized semantic meaning across all disciplines.