Long Left Right Arrow in LaTeX (\longleftrightarrow)

Where it is used

Draws a long two-headed single arrow, a stretched \leftrightarrow for correspondences between long expressions.

\longleftrightarrow suits a correspondence between two lengthy objects, for example a bijection between subsets and binary strings, where the short arrow looks lost. It is a fixed-length symbol, so labels need \overset or a stacked construction. Note that \iff is built from the double-shafted \Longleftrightarrow, not from this single-shaft version, so do not use \longleftrightarrow for logical equivalence in proofs. Physics uses it for a duality between two theories. The extra length also helps when the arrow carries text stacked above it.

Minimal compilable example

Paste this into an empty .tex file and compile it with pdfLaTeX, XeLaTeX or LuaLaTeX.

\documentclass{article}
\begin{document}
Long Left Right Arrow: $\longleftrightarrow$

\[ \{S \subseteq [n]\} \longleftrightarrow \{0, 1\}^n \]
\end{document}

Related symbols

• Up Down Arrow\updownarrow
• Left Right Arrow\leftrightarrow
• Left Right Arrow (Double)\Leftrightarrow
• Down Arrow (Double)\Downarrow
• Long Left Right Arrow (Double)\Longleftrightarrow
• Long Right Arrow (Double)\Longrightarrow

Frequently asked questions

How do I write Long Left Right Arrow in LaTeX?

Type \longleftrightarrow in math mode, for example $\{S \subseteq [n]\} \longleftrightarrow \{0, 1\}^n$. It works in plain LaTeX without loading any package.

Which package do I need for \longleftrightarrow?

None. \longleftrightarrow is part of standard LaTeX, so it compiles with nothing in the preamble but the document class.

Can I use \longleftrightarrow in text mode, or only in math mode?

Only in math mode. Outside $...$ LaTeX stops with "Missing $ inserted", so write $\longleftrightarrow$ in running text. If you only need the glyph in text, paste the Unicode character ⟷ instead (with XeLaTeX or LuaLaTeX and a font that has it).