Font sizes, families and styles.

Introduction

LaTeX normally chooses the appropriate font and font size based on the logical structure of the document (e.g. sections). In some cases, you may want to set fonts and sizes by hand.

The following example shows how to use the smallest available font size in LaTeX (\tiny) and the small caps (\textsc{...}) font style:

This is a simple example, {\tiny this will show different font sizes} and also \textsc{different font styles}.

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The following image shows the output produced by the example above:

This is a simple example, this will show different font sizes and also different font styles.

Font sizes

Font sizes are identified by special names, the actual size is not absolute but relative to the font size declared in the \documentclass statement (see Creating a document in LaTeX).

In the following example, {\huge huge font size} declares that the text inside the braces must be formatted in a huge font size. For a complete list of available font sizes see the reference guide.

In this example the {\huge huge font size} is set and 
the {\footnotesize Foot note size also}. There's a fairly 
large set of font sizes.

In this example the huge font size is set and the Foot note size also. There’s a fairly large set of font sizes.

Font families

By default, in standard LaTeX classes the default style for text is usually a Roman (upright) serif font. To use other styles (families) such as sans serif, typewriter (monospace) etc. you need to use some specific LaTeX commands, as shown in the example below:

In this example, a command and a switch are used. 
\texttt{A command is used to change the style 
of a sentence}.

\sffamily
A switch changes the style from this point to 
the end of the document unless another switch is used.

In this example, a command and a switch are used.  A command is used to change the style of a sentence.

A switch changes the style from this point to the end of the document unless another switch is used.

You can set up the use of sans font as a default in a LaTeX document by using the command:

\renewcommand{\familydefault}{\sfdefault}

Similarly, for using roman font as a default:

\renewcommand{\familydefault}{\rmdefault}

Font styles

The most common font styles in LaTeX are bold, italics and underlined, but there are a few more.

In the following example the \textsl command sets the text in a slanted style which makes the text look a bit like italics, but not quite. See the reference guide for a complete list of font styles.

Part of this text is written \textsl{in a different font style} to highlight it.

The following image shows the output produced by the example above:

Part of this text is written in a different font style to highlight it.

If you want to go back to "normal" font style (default for the LaTeX class you are using), this can be done by using the \textnormal{...} command or the \normalfont switch command.

Reference guide

Font sizes

Command	Output
{\tiny 123}	123
{\scriptsize 123}	123
{\footnotesize 123}	123
{\small 123}	123
{\normalsize 123}	123
{\large 123}	123
{\Large 123}	123
{\LARGE 123}	123
{\huge 123}	123
{\Huge 123}	123

Default font familie

See "Special Characters In Latex".

Font styles

Command	Switch	Output
\textmd{Sample Text 0123}	\mdseries	Sample Text 0123
\textbf{Sample Text 0123}	\bfseries	Sample Text 0123
\textup{Sample Text 0123}	\upshape	Sample Text 0123
\textit{Sample Text 0123}	\itshape	Sample Text 0123
\textsl{Sample Text 0123}	\slshape	Sample Text 0123
\textsc{Sample Text 0123}	\scshape	Sample Text 0123

Source: https://www.overleaf.com/learn/latex/Font sizes, families, and styles