LaTeX Bold & Italic
\textbf for bold, \textit for italic, \emph for semantic emphasis, \bm for bold math.
The cheat sheet
\textbf{bold text} % bold
\textit{italic text} % italic
\emph{emphasis} % semantic italic (toggles)
\textbf{\textit{bold italic}} % both at once
\underline{underlined} % underline (avoid in print)
% In math mode:
\usepackage{bm}
$\bm{\alpha}, \bm{x}^2$ % bold math symbols
$\boldsymbol{\alpha}$ % alternative (amsmath)The four formatting commands compared
| Command | Effect | When to use |
|---|---|---|
| \textbf{} | Bold | Strong emphasis, defined terms |
| \textit{} | Italic | Book titles, foreign phrases |
| \emph{} | Italic (or roman if nested) | Semantic emphasis in body text |
| \underline{} | Underline | Almost never (looks dated) |
Bold math (the gotcha)
\textbf{} doesn't work inside math mode — $\textbf{x}$ renders bold roman text, not bold math. For real bold math symbols:
\usepackage{bm} % the bm package handles all cases
% Bold variables, vectors, matrices
$\bm{x}, \bm{y}, \bm{A}$
% Bold Greek letters
$\bm{\alpha}, \bm{\beta}, \bm{\Sigma}$
% Bold operators
$\bm{\nabla} f$Common mistakes
- Using
\bfinstead of\textbf.\bfis old, unscoped, and breaks combinations. Use\textbf. - Trying
\textbfin math mode. Doesn't work. Use\bmor\boldsymbol. - Underlining body text. Looks unprofessional in print and doesn't wrap. Use
\emphor\textitinstead. - Forgetting to load the bm package. Bold math requires
\usepackage{bm}.
*bold text* // bold
_italic text_ // italic
*_bold italic_* // both
// Bold math
$ bold(x) + bold(y) = bold(z) $
$ bold(alpha) $ // bold GreekMarkdown-style stars and underscores. Bold math is just bold(x). Try TypeTeX free.
Frequently Asked Questions
Use \textbf{your text}. Example: 'This is \textbf{bold} text.' Works inline anywhere in the document. For bold math, use \boldsymbol{} (with the amsmath package) or \bm{} (with the bm package).
Use \textit{your text} for italic, or \emph{your text} for semantic emphasis (which is italic by default but can be redefined). For book titles and similar conventions, prefer \emph because it nests correctly: \emph{italic with \emph{nested} non-italic word}.
\textit always produces italic. \emph means 'emphasize' and toggles between roman and italic based on context — if you nest \emph inside another \emph, the inner one becomes roman (back to upright) for visual contrast. For body-text emphasis, use \emph; for italic as a typographic choice (book titles, foreign words), use \textit.
Nest the commands: \textbf{\textit{bold and italic}} or \textit{\textbf{bold and italic}}. Order doesn't matter for visual output. For semantic emphasis with bold, use \textbf{\emph{...}}.
Use the bm package (best): \usepackage{bm}, then \bm{\alpha} for bold alpha. Alternative: \boldsymbol{\alpha} from amsmath. Plain \textbf{} doesn't work in math mode. For bold Greek letters specifically, \bm{} is the most reliable.
\bf is the old-style 'switch to bold for the rest of this group' command. \textbf{} is the modern command-with-argument form. Use \textbf{} — it's safer (scoped to its argument) and combines correctly with other formatting. \bf is technically deprecated.
Use \underline{your text}. Note: underlines look bad in formal typesetting and don't break across line ends. For long underlines that wrap, use the soul package: \usepackage{soul} then \ul{long text that may wrap}.
Section headings are bold by default in standard classes. To customize, use the titlesec package: \usepackage{titlesec} \titleformat{\section}{\Large\bfseries}{\thesection}{1em}{}. \bfseries is the declarative form of \textbf for heading scopes.
Yes — most modern fonts have a bold-italic style. Use \textbf{\textit{text}} or the textcomp package's \textbi{} where supported. With newtxtext, bold-italic Times is built in. With Computer Modern, it works automatically.