doublearrow

Doublearrow, or double arrow, is a general term for symbols that depict two arrows pointing in opposite directions. The most common glyphs are the left-right arrow (↔) and the left-right double arrow (⇔). The term is informal and can refer to any two-headed arrow used to convey bidirectionality, reciprocity, or a two-way relation in different contexts.

In mathematics and logic, the symbol ⇔ (left-right double arrow) is typically used to denote logical equivalence or a biconditional, meaning that P holds if and only if Q holds. It expresses mutual implication between two statements. The simpler ↔ (left-right arrow) is used more broadly to indicate a bidirectional relation, such as definitions, mappings, or reversible processes, where each side is connected to the other.

Encoding and typography: these symbols have specific Unicode points. ↔ is U+2194, and ⇔ is U+21D4. HTML named entities include ↔ for ↔ and ⇔ for ⇔. In LaTeX, \leftrightarrow produces ↔ and \Leftrightarrow produces ⇔. In software interfaces, a double-arrow glyph can be used to signify bidirectional navigation or reversible operations, though the exact glyph may vary by font and platform.

See also: Arrows, Biconditional, Equivalence relation, Bidirectional mapping, Reversible process, Unicode arrows.

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