Surjective in LaTeX (\twoheadrightarrow)

Where it is used

Arrow with a double head, marking a surjective (onto) map or morphism.

Algebraists write f\colon A \twoheadrightarrow B to say f is onto, for example the quotient map G \twoheadrightarrow G/N. It pairs with \hookrightarrow for injections, so a short exact sequence 0 \to A \hookrightarrow B \twoheadrightarrow C \to 0 shows both at a glance. There is a leftward version, \twoheadleftarrow, for maps drawn in the other direction. The arrow is a relation, so spacing around it is automatic. Avoid using it to mean convergence or implication; \to and \implies are standard there.

Minimal compilable example

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

\documentclass{article}
\usepackage{amssymb}
\begin{document}
Surjective: $\twoheadrightarrow$

\[ \pi\colon G \twoheadrightarrow G/N \]
\end{document}

Related symbols

• Left Right Arrow\leftrightarrow
• Hook Right Arrow\hookrightarrow
• Restrictionf|_A
• Range\text{range}(f)
• Function Evaluationf(x) = y
• Codomain\text{cod}(f)

Frequently asked questions

How do I write Surjective in LaTeX?

Type \twoheadrightarrow in math mode, for example $\pi\colon G \twoheadrightarrow G/N$. Load amssymb first with \usepackage{amssymb}.

Which package do I need for \twoheadrightarrow?

\twoheadrightarrow needs amssymb: add \usepackage{amssymb} to your preamble before the document starts.

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

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