You have come to the right place. In this content, the calligraphic font style is represented by `\mathcal{}`

command.

For your convenience, various problems have been solved, which you face.

However, this command is only valid for math mode.

## Use mathcal command for Calligraphic font

Usage of this symbol is much more in terms of usage. From mathematically normal distribution to Big o notation and topology.

```
\documentclass{article}
\begin{document}
\[ ABCDEF \quad \mathcal{ABCDEF} \]
\[ \mathcal{O},\mathcal{T},\mathcal{P},\mathcal{N} \]
\[ \mathcal{N}\quad\mathcal{A}f(x)\quad\mathcal{F} \]
\[ X^2/\sigma^2 \sim \mathcal{X}^2(\mu^2/\sigma^2) \]
\[ \ln \mathcal{L}(\mu ,\sigma^2) \]
\end{document}
```

**Output : **

## Lowercase Calligraphic fonts

`\mathcal{}`

commands have some limitations. Because even if the capital alphabet is converted to this font. Cannot convert digits and small alphabets to calligraphy fonts.

```
\documentclass{article}
\usepackage{amssymb}
\begin{document}
\[ \verb|\mathcal{abcd}|\dashrightarrow \mathcal{abcd} \]
\[ \verb|\mathcal{1234}|\dashrightarrow\mathcal{1234} \]
\[ \verb|\mathcal{ABCDefgh}|\dashrightarrow\mathcal{ABCDefgh} \]
\end{document}
```

**Output : **

## Calligraphic bold font style

You will see many commands that convert text or math expressions to bold font style like `\textbf{}`

, `\mathbm`

, `bf`

etc.

However, in case of calligraphy font style, `\boldsymbol`

should be used which will convert font style of symbol to bold.

Because if you use another command instead of `\boldsymbol`

, output will show an arrow.

```
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[ S\in \boldsymbol{\mathcal{P}}_d \]
\[ \theta,x\in\boldsymbol{\mathcal{X}} \]
\[ \boldsymbol{\mathcal{P}}(X)\in\boldsymbol{\mathcal{X}} \]
\end{document}
```

**Output : **

## Big O notation and topology T denoted by mathcal command

Below are some examples of Big O notation and Topology T by this command.

```
\documentclass{article}
\begin{document}
\[ \mathcal{O},\;\mathcal{T} \]
\[ \mathcal{O}(|K|.g)=\mathcal{O}(g)\quad Q_i\in \mathcal{T} \]
\[ \mathcal{O}(\log n)\quad (\mathcal{T}_1 ,\mathcal{T}_2) \]
\[ \mathcal{O}(n^c)\quad (X,\mathcal{T}_2)\rightarrow (X,\mathcal{T}_1) \]
\[ f(n) = \mathcal{O}(n!) \]
\end{document}
```

**Output : **