How to write a union symbol in LaTeX

# How to write a union symbol in LaTeX

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This article aims to show you a simple way to create a union symbol in LaTeX.

In Mathematics you have the set operators, and sometimes when you are working with intervals or sets in math you may see the Union symbol. That’s why today you will learn how to insert it in your LaTeX document.

## Union Symbol

The union symbol is used in set theory, which represents one of the fundamental operations to combine two sets, known as union operation. If we have set A and set B, the union is defined as A U B, for example,

$$A\cup B=\{x\,:\, x \in A \text{ or } x \in B\}$$


## Union Symbol in LaTeX

LaTeX has the standard union symbol built-in, it takes no value as argument, the command is \cup

\begin{document}
$$A \cup \left( B \cup C \right)$$
\end[document}


Of course we are not limited to just one size of the symbol, and we can adjust it a little bit more, adding maybe superscripts or subscripts, for other notations used in set theory, for example

\begin{document}
$$\cup_{i=1}^{n}S_{i}$$
\end[document}


## Big Union symbol

You can also insert the union symbol using the command \bigcup, the output is a bigger symbol,

\begin{document}
$$\bigcup_{i=1}^{n}S_{i}$$
\end{document}


Another alternative to write the big union symbol along with the limits, is to use the command \limits before \bigcup, the output results in

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


Notice that the command \bigcup\limits generated a smaller symbol than the command \bigcup. Personally I prefer the former option.

Lastly, there are some variations of the union symbols define as the disjoint union symbol, to generated them we have the following commands respectively,

\documentclass{article}\begin{center}
Disjoint union symbol
$$A \sqcup B$$
$$A \dot{\cup} B$$
$$A \bigsqcup B$$
$$A \uplus B$$
\end{center}


There could be packages that generated this symbol with other commands, but if you already have them by default use it already.

Now you have the knowledge of the different types of union symbols out there, and how to insert them into your document.

I hope you find this post useful and as always, keep writing in LaTeX. 