How to Typeset the Union Symbol in LaTeX

Correctly typeset the union symbol in LaTeX to include it in your document according to its context.
  • Updated

The union symbol is used in mathematics to represent the union of two sets. It’s used in many areas of mathematics, including set theory, graph theory, and topology. It is also commonly used in computer science and engineering. In addition to its mathematical uses, the union symbol can also be used in text to represent the concept of “or”.

In this article, we will explore the different options for how to include the union symbol so you can include it in your LaTeX document according to its context.

There are two main options for typesetting the union symbol in LaTeX:

  1. Using the built-in \cup command.
  2. Using the amsmath package.

Using the default Union symbol in LaTeX

The \cup command is a built-in LaTeX command used to typeset the union symbol in LaTeX. Simply enclose the symbol in dollar signs to typeset it inline mode, or in double dollar signs to typeset it in display mode.

\documentclass{article}

\begin{document}

$A\cup B$ is an example of an inline mode. Below is the display mode.

$$A\cup B$$

\end{document}

\(A\cup B \ \text{is an example of an inline mode. Below is the display mode.}\)

\(A\cup B\)

Big Union symbol

The \bigcup command is a built-in command in LaTeX used to write a big union symbol. It is used when the union is taken over an index set or a collection of sets.

Take a look at the code below:

$A\bigcup B$ is an example of an inline mode. Below is the display mode.

$$A\bigcup B$$

\(A\bigcup B \ \text{is an example of an inline mode. Below is the display mode.}\)

\(A\bigcup B\)

Here is another example:

\begin{center}
    Set of natural numbers $\bigcup\limits_{i=1}^{\infty}A_{i}$
\end{center}

\(\text{Set of natural numbers} \bigcup\limits_{i=1}^{\infty}A_{i}\)

Variations of the union symbol

There are several variations of the union symbol, each with a slightly different meaning or usage. Here are the most common variations:

Disjoint union symbol
    $$A \sqcup B$$
    $$A \dot{\cup} B$$
    $$A \bigsqcup B$$
    $$A \uplus B$$

\(A\sqcup B\)

\(A\dot{\cup} B\)

\(A\bigsqcup B\)

\(A\uplus B\)

Customizing the symbol

You can also customize the appearance of the union symbol by changing its size, color, or font. This can be done using LaTeX commands such as \Large or \textcolor.

Using the amsmath package

The amsmath package is a LaTeX package that provides a wide range of mathematical symbols and formatting options. Once you have it included in your document’s preamble, you can use its various commands and options to typeset mathematical symbols and equations.

To typeset the union symbol with the amsmath package in LaTeX, you can use the following code:

\usepackage{amsmath}

\[A \cup B\]

In addition to the \cup command, the package also provides other commands for typesetting mathematical symbols, such as the intersection symbol (\cap), the disjoint union symbol (\sqcup), and the Cartesian product symbol (\times).

Final thoughts

Which method you should choose to typeset the union symbol in LaTeX will depend on the context in which it will be used in your document. Choose one and be consistent with it throughout your LaTeX document.

In general, if you just need the union symbol in a basic format, the default symbol is a good choice. On the other hand, if you need more customization options or if you are already using the amsmath package, then using it is a good choice.

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