Empty Set in LaTeX: emptyset vs varnothing

To write the empty set in LaTeX, use $\emptyset$ (available in standard LaTeX) or $\varnothing$ (an AMS symbol that needs the amssymb package). Both render the empty-set symbol in math mode; \varnothing is the form many authors prefer for its look.

What it is used for in research

The empty set, the set with no elements, appears in set-theoretic statements such as A \cap B = \emptyset (two sets are disjoint), in probability (the impossible event) and in definitions of sigma-algebras and topologies. Anyone typesetting a thesis, paper or problem set in these areas needs a reliable way to produce it. For neighbouring set notation see our guides on set intersection in LaTeX, subset symbols in LaTeX and blackboard bold (mathbb).

Install or access (official source only)

\emptyset is part of standard LaTeX and needs no package. \varnothing comes from the AMS symbol fonts. The AMS Short Math Guide for LaTeX (distributed on CTAN) states that most of its features come with the amssymb and amsmath packages, and its own source begins with \usepackage{amssymb,amsmath}. CTAN’s amsfonts page identifies amssymb as the package that defines the names of the individual symbols. Any current TeX distribution that ships the AMS packages gives you these; there is nothing to buy.

Step-by-step: typing the symbol

1. Add \usepackage{amssymb} (and, for equations, \usepackage{amsmath}) to your preamble, after \documentclass.
2. Switch to math mode: $...$ inline, or \[ ... \] for a displayed equation.
3. Type \emptyset or \varnothing.
4. Compile as usual.

A minimal example:

\documentclass{article}
\usepackage{amssymb,amsmath}
\begin{document}
Sets $A$ and $B$ are disjoint if $A \cap B = \emptyset$.
Equivalently, $A \cap B = \varnothing$.
\end{document}

Output and how to read it

Both commands print a circle with a diagonal slash, the empty-set sign. The Comprehensive LaTeX Symbol List notes that “many people prefer the look of AMS’s \varnothing (Table 402) to that of LaTeX’s \emptyset”, so choose one and use it consistently throughout a document. The AMS Short Math Guide lists both commands in its miscellaneous symbols table.

Empty set in LaTeX: \emptyset vs \varnothing

Command	Needs	Source
\emptyset	Standard LaTeX math mode	Comprehensive LaTeX Symbol List; AMS Short Math Guide
\varnothing	amssymb (AMS symbol font)	Comprehensive LaTeX Symbol List, Table 402; AMS Short Math Guide
\emptysetobar, \emptysetoarr, \emptysetocirc, \emptysetoarrl, \revemptyset	The stix package	Comprehensive LaTeX Symbol List, Table 389 “stix Empty Sets”

The same stix table also lists \emptyset and \varnothing. The stix variants are for specialised notations; ordinary documents need only the first two rows.

Troubleshooting

Undefined control sequence for \varnothing

Because \varnothing is documented as an AMS symbol, the most likely cause is that amssymb is not loaded. Add \usepackage{amssymb} to the preamble. (This is our inference from the AMS labelling, not a message quoted from the documentation.) Using \emptyset avoids the dependency.

Symbol looks like a different character

The Comprehensive LaTeX Symbol List warns that the MnSymbol package defines \emptyset and \varnothing as synonyms for \diameter. If you load MnSymbol, the result may differ from what you expect. It also cautions that some authors use \varnothing x or \diameter x for other meanings, and advises explaining your notation.

Symbol appears as text instead of math

Both commands are math-mode symbols. Place them inside $...$ or a math environment.

Free alternatives

Option	When to use it
\emptyset	You want no extra packages
\varnothing with amssymb	You prefer the AMS appearance and already use AMS packages
stix empty-set variants	You need one of the specialised forms in Table 389

For other symbols, see LaTeX math signs and Greek symbols in LaTeX.

FAQ

How do I write the empty set in LaTeX?

Type $\emptyset$ or, with amssymb loaded, $\varnothing$, inside math mode.

Do I need a package for the empty set in LaTeX?

Not for \emptyset. \varnothing is an AMS symbol, so load amssymb.

Which looks better, \emptyset or \varnothing?

That is a matter of taste; the Comprehensive LaTeX Symbol List says many people prefer the look of \varnothing. Pick one and keep it consistent.

Sources (official documentation)

• AMS Short Math Guide for LaTeX, on CTAN: tug.ctan.org/info/short-math-guide/short-math-guide.pdf (read 2026-11-07)
• The Comprehensive LaTeX Symbol List, on CTAN: mirrors.ctan.org/info/symbols/comprehensive/symbols-a4.pdf (read 2026-11-07)
• CTAN amsfonts package page: ctan.org/pkg/amsfonts (read 2026-11-07)