Math fonts in LaTeX: bold, blackboard, calligraphic

Q: How do I write the set of real numbers ℝ in LaTeX?

Load amssymb and write \mathbb{R}. The same works for ℕ, ℤ, ℚ and ℂ with \mathbb{N}, \mathbb{Z}, \mathbb{Q} and \mathbb{C}.

Q: Why does \mathbf not make my Greek letter bold?

In LaTeX, \mathbf only changes Latin letters, digits and capital Greek letters. Use \boldsymbol{\alpha} or \bm{\alpha} for a bold α.

Q: How do I write the d of an integral upright?

Write \mathrm{d}x, and put a thin space \, before it: \int f(x)\,\mathrm{d}x.

Use a math alphabet command: \mathbf{v} for bold, \mathbb{R} for blackboard bold (amssymb), \mathcal{L} for calligraphic and \mathfrak{g} for Fraktur; \boldsymbol or \bm also makes Greek letters and symbols bold.

Math alphabets

In math mode, letters are italic variables. A math alphabet command changes the style of the letters in its argument, often to give them a meaning: bold for vectors and matrices, blackboard bold for number sets, calligraphic for families of sets.

Command	Result	Typical use
`\mathbf{v}`	upright bold	vectors, matrices
`\boldsymbol{\alpha}`, `\bm{\alpha}`	bold, keeps italic, also for Greek and symbols	bold Greek vectors
`\mathbb{R}`	blackboard bold (amssymb)	ℕ, ℤ, ℚ, ℝ, ℂ
`\mathcal{L}`	calligraphic capitals	Lagrangians, families of sets
`\mathfrak{g}`	Fraktur	Lie algebras, ideals
`\mathrm{d}`	upright roman	units, the differential d, labels
`\mathit{x}`	italic	multi-letter variable names
`\mathsf{T}`	sans serif	transpose, categories
`\mathtt{x}`	typewriter	code in formulas

The common alphabets

LaTeXPreamble: \usepackage{amssymb,bm}Open in editor

\mathbf{A}\mathbf{x} = \mathbf{b} \qquad \bm{\mu} \in \mathbb{R}^{44} \qquad
\mathcal{L}(\theta) \qquad \mathfrak{su}(2) \qquad
\int f(x) \, \mathrm{d}x \qquad \mathbf{X}^{\mathsf{T}}

For words inside a formula, use \text{..} from amsmath, not a math alphabet: \text keeps the spaces between words.

Words in a formula

LaTeXOpen in editor

f(x) = \begin{cases} 1 & \text{if } x \ge 44, \\ 0 & \text{otherwise.} \end{cases}

Math styles

\displaystyle, \textstyle, \scriptstyle and \scriptscriptstyle switch the size of everything after them inside the current group: a fraction in running text, for example, can be set at display size.

A display-size fraction in a line of text

LaTeXOpen in editor

Compare $\frac{1}{2}$ with $\displaystyle\frac{1}{2}$ in the same line,
and a sum $\sum_{i=1}^{n} x_i$ with $\displaystyle\sum_{i=1}^{n} x_i$.

All style commands

The grid shows each command applied to the letters "Ab". Click a copy button to copy the command.

\displaystyle
\textstyle
\scriptstyle
\scriptscriptstyle
\bf
\rm
\it
\sf
\frak
\tt
\cal
\bold
\mathbf
\bm
\boldsymbol
\pmb
\mathrm
\mathit
\mathnormal
\mathsf
\mathfrak
\mathtt
\Bbb
\mathbb
\mathcal
\mathbin
\mathclose
\mathinner
\mathop
\mathopen
\mathord
\mathpunct
\mathrel
\Huge
\normalsize
\huge
\small
\footnotesize
\Large
\LARGE
\scriptsize
\large
\tiny

What does not work

Greek letters and accents.
Text formatting for bold and italic in ordinary text.
bm and amssymb; the alphabets are described in the amsfonts documentation on CTAN.

Questions and answers

How do I write the set of real numbers ℝ in LaTeX?

Load amssymb and write \mathbb{R}. The same works for ℕ, ℤ, ℚ and ℂ with \mathbb{N}, \mathbb{Z}, \mathbb{Q} and \mathbb{C}.

Why does \mathbf not make my Greek letter bold?

In LaTeX, \mathbf only changes Latin letters, digits and capital Greek letters. Use \boldsymbol{\alpha} or \bm{\alpha} for a bold α.

How do I write the d of an integral upright?

Write \mathrm{d}x, and put a thin space \, before it: \int f(x)\,\mathrm{d}x.

Every example on this page is typeset by Scissor LaTeX when the site is built. Last updated 2026-11-07.