No font:
$$
ABCDEFGHIJKLMNOPQRSTUVWXYZ \\\\
abcdefghijklmnopqrstuvwxyz
$$
Math Boldface
`\mathbf{ }`
$$
\mathbf{ABCDEFGHIJKLMNOPQRSTUVWXYZ} \\\\
\mathbf{abcdefghijklmnopqrstuvwxyz}
$$
Math Italic
`\mathit{ }`
$$
\mathit{ABCDEFGHIJKLMNOPQRSTUVWXYZ} \\\\
\mathit{abcdefghijklmnopqrstuvwxyz}
$$
Math Roman
`\mathrm{ }`
$$
\mathrm{ABCDEFGHIJKLMNOPQRSTUVWXYZ} \\\\
\mathrm{abcdefghijklmnopqrstuvwxyz}
$$
Math Fraktur
`\mathfrak{ }`
$$
\mathfrak{ABCDEFGHIJKLMNOPQRSTUVWXYZ} \\\\ \mathfrak{abcdefghijklmnopqrstuvwxyz}
$$
Math Caligraphic
`\mathcal{ }`
$$
\mathcal{ABCDEFGHIJKLMNOPQRSTUVWXYZ} \\\\
\mathcal{abcdefghijklmnopqrstuvwxyz}
$$
Math Script
`\mathscr{ }`
$$
\mathscr{ABCDEFGHIJKLMNOPQRSTUVWXYZ} \\\\
\mathscr{abcdefghijklmnopqrstuvwxyz}
$$
Math Blackboard Bold
`\mathbb{ }`
$$
\mathbb{ABCDEFGHIJKLMNOPQRSTUVWXYZ} \\\\
\mathbb{abcdefghijklmnopqrstuvwxyz}
$$