Left Arrow in LaTeX (\leftarrow)

Where it is used

Draws a short single arrow pointing left, used for assignment in algorithms and reversed maps.

Pseudocode writes assignment as x \leftarrow x + 1, and \gets is a built-in alias for exactly this arrow, which reads more naturally in algorithm listings. In mathematics it sometimes shows a map written right to left, B \leftarrow A, or a limit approached from the right in older texts. Machine learning papers use it for parameter updates, \theta \leftarrow \theta - \eta g. It is a relation, so TeX adds thick spacing around it. For a longer arrow use \longleftarrow, and for a labeled one the extensible \xleftarrow{text}.

Minimal compilable example

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

\documentclass{article}
\begin{document}
Left Arrow: $\leftarrow$

\[ \theta \leftarrow \theta - \eta \nabla_\theta L(\theta) \]
\end{document}

Related symbols

• Right Arrow\rightarrow
• Up Arrow\uparrow
• Long Left Arrow\longleftarrow
• Long Right Arrow\longrightarrow
• Down Arrow\downarrow
• Left Arrow (Double)\Leftarrow

Frequently asked questions

How do I write Left Arrow in LaTeX?

Type \leftarrow in math mode, for example $\theta \leftarrow \theta - \eta \nabla_\theta L(\theta)$. It works in plain LaTeX without loading any package.

Which package do I need for \leftarrow?

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

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

Only in math mode. Outside $...$ LaTeX stops with "Missing $ inserted", so write $\leftarrow$ 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).