Function in LaTeX (f(x))

Where it is used

Function f applied to an argument x, the basic notation for a function value.

Single-letter names like f, g and h are set in italic, which is correct for symbols that stand for functions. Multi-letter named functions are different: write \sin x or \log x, and for your own names use \operatorname{softmax}(z) so they print upright instead of as a product of italic letters. In optimization, f(x) is often the objective, as in \min_x f(x) subject to constraints. When the argument is tall, use \left( \right) or \bigl( \bigr) to size the parentheses. For vector arguments, f(\mathbf{x}) with a bold x is common.

Also listed under: Optimization

Minimal compilable example

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

\documentclass{article}
\begin{document}
Function: $f(x)$

\[ f(x) = x^3 - 2x + 1 \]
\end{document}

Related symbols

• Function Definitionf: A \to B
• Maps To\mapsto
• Approaches\to
• Long Right Arrow\longrightarrow
• Compositionf \circ g
• Inverse Functionf^{-1}

Frequently asked questions

How do I write Function in LaTeX?

Type f(x) in math mode, for example $f(x) = x^3 - 2x + 1$. It works in plain LaTeX without loading any package.

Which package do I need for f(x)?

None. f(x) is part of standard LaTeX, so it compiles with nothing in the preamble but the document class.

Can I use f(x) in text mode, or only in math mode?

Both. f(x) compiles in running text as well as inside $...$; in a formula keep it in math mode so it gets math fonts and spacing.