Asterisk in LaTeX (\ast)

Where it is used

Asterisk as a binary operator, typically for convolution or a generic group operation.

In math mode \ast is the same glyph as typing *, a binary operator with medium spacing, used for convolution (f \ast g)(t) = \int f(\tau) g(t - \tau)\,d\tau and for generic binary operations in algebra. As a superscript, A^* or A^\ast denotes adjoint, conjugate transpose, dual space or Kleene star depending on the field. It sits centered on the math axis, unlike the raised text asterisk. For a starred optimal value x^\star some authors prefer \star to keep the meanings apart.

Also listed under: Computer Science

Minimal compilable example

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

\documentclass{article}
\begin{document}
Asterisk: $\ast$

\[ (f \ast g)(t) = \int_{-\infty}^{\infty} f(\tau)\, g(t - \tau)\, d\tau \]
\end{document}

Related symbols

• Composition\circ
• Star\star
• Bullet\bullet
• Circle Slash\oslash
• Diamond\diamond
• Circle Minus\ominus

Frequently asked questions

How do I write Asterisk in LaTeX?

Type \ast in math mode, for example $(f \ast g)(t) = \int_{-\infty}^{\infty} f(\tau)\, g(t - \tau)\, d\tau$. It works in plain LaTeX without loading any package.

Which package do I need for \ast?

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

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

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