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Quick answer: in LaTeX math mode, type ( and ) directly for parentheses, [ and ] for square brackets, and \{ and \} for curly braces (a bare { is grouping and prints nothing). To make the delimiters grow with their contents, wrap them in \left and \right; to set a size yourself, use \big, \Big, \bigg or \Bigg. Syntax below follows Overleaf’s “Brackets and Parentheses” documentation, read 2026-11-08.
What parentheses and brackets are used for in research writing
Equations in papers, theses and statistical methods sections routinely nest grouping symbols: function arguments, intervals, sets, inner products, norms and fractions inside brackets. LaTeX has a command for each delimiter and two ways of controlling its size, and most formatting errors come from mixing those up. This guide is a task reference for authors who already have a working LaTeX document; see the related guides on absolute value, floor and ceiling and vertical lines for delimiters with their own conventions.
Are () brackets or parentheses? Basic delimiters
Strictly, () are parentheses (round brackets) and [] are square brackets; in American usage “brackets” alone usually means square brackets, while Overleaf’s table labels each type by both names. The delimiters Overleaf lists for math mode, with their markup, are:
| Symbol name | What you type |
|---|---|
| Parentheses; round brackets | (x+y) |
| Brackets; square brackets | [x+y] |
| Braces; curly brackets | \{ x+y \} |
| Angle brackets | \langle x+y \rangle |
| Pipes; vertical bars | |x+y| |
| Double pipes | \|x+y\| |
Source: Overleaf, Brackets and Parentheses, read 2026-11-08.
When to use [] versus ()?
In LaTeX the two are typed the same way and differ only in meaning, which your field decides: for example, parentheses and square brackets are commonly used to mark open and closed ends of an interval. LaTeX does not enforce either convention, so choose the one your discipline or journal style requires and apply it consistently.
How to get {} to show in LaTeX
Type a backslash before each brace: \{ x+y \}. Without the backslash, { } only groups material for LaTeX and nothing is printed. The same table shows that sized versions follow the same pattern, for example \bigl\{, \Bigl\{, \biggl\{ and \Biggl\{ (Overleaf, 2026-11-08).
Automatic sizing with \left and \right
To make a delimiter match the height of what it encloses, put \left before the opening symbol and \right before the closing one. Overleaf’s example, which also answers “parentheses around a fraction”:
\[ F = G \left( \frac{m_1 m_2}{r^2} \right) \]Overleaf states: “Even if you are using only one bracket, both commands are mandatory.” If you want only one visible delimiter, pair the real one with an invisible one (see the multi-line section).
Manual sizes: \big, \Big, \bigg, \Bigg
When you want a specific size rather than an automatic one, use the four size commands, from smallest to largest: \big, \Big, \bigg, \Bigg. Add l or r to mark the left or right side of a pair. Overleaf’s example:
\[ \Biggl \langle 3x+7 \biggr \rangle \]Overleaf explains that \Biggl and \biggr establish the size of the left and right angle brackets respectively. Its reference list includes \bigl(, \Bigl(, \biggl(, \Biggl( on the left and \bigr], \Bigr], \biggr], \Biggr] on the right. Sizes need not match within one equation, which is why this is the tool for a deliberately larger outer bracket.
Decision aid: which form to use
| Situation | Use | Source basis |
|---|---|---|
| Delimiters around a short expression such as x+y | Plain ( ), [ ], \{ \} |
Overleaf basic-delimiter table |
| Delimiters around a tall expression such as a fraction | \left … \right |
Overleaf automatic-sizing example |
| You need an exact, chosen size, or different sizes on each side | \bigl, \Bigr, \biggl, \Biggr and similar |
Overleaf manual-size reference |
| Expression broken across lines in align, align* or aligned | \right. at the end of the first line and \left. at the start of the next |
Overleaf multi-line section |
Multi-line equations
Overleaf documents that in align, align* and aligned, the \left and \right commands “must be balanced on each line and on the same side of &”. This fails because the bracket opened on line one is not closed on that line:
y = 1 + & \left( \frac{1}{x} + \frac{1}{x^2} + \frac{1}{x^3} + \ldots \\
& \quad + \frac{1}{x^{n-1}} + \frac{1}{x^n} \right)The fix is an invisible delimiter, written as a period: add \right. at the end of the first line and \left. at the start of the second line after the &.
y = 1 + & \left( \frac{1}{x} + \frac{1}{x^2} + \frac{1}{x^3} + \ldots \right. \\
&\left. \quad + \frac{1}{x^{n-1}} + \frac{1}{x^n} \right)See aligned equations in LaTeX for the alignment environments themselves, and matrices in LaTeX for matrices that need bracketed delimiters.
Install or access (official source only)
These commands are standard LaTeX math-mode syntax, so you need a LaTeX system or an online editor. Use the official sources: the online editor at Overleaf, or a local distribution such as TeX Live (TeX Users Group) or MiKTeX. The \left, \right and \big-family commands are part of core LaTeX; the mathtools package (CTAN) adds extras and is loaded with \usepackage{mathtools}.
Step-by-step: typing and sizing delimiters
- Open a document and enter math mode, for example
\[ ... \]or$ ... $. - Type plain parentheses
( )and square brackets[ ]directly. - For curly braces, put a backslash before each:
\{ x+y \}. - If the enclosed content is tall (a fraction, for example), put
\leftbefore the opening delimiter and\rightbefore the closing one:\left( \frac{m_1 m_2}{r^2} \right). Both commands are required as a pair. - If you want one visible delimiter only, pair it with an invisible one:
\left. ... \right). - If you need a specific size instead of automatic sizing, use
\big,\Big,\biggor\Bigg, withlorradded for opening or closing delimiters (for example\Biggl\langle). - Compile and check the output against the expected size and pairing.
Output and how to read it
With \left and \right, the delimiter height follows the tallest item inside it; with \big-family commands it is fixed at the size you named. A quick check: compile a one-line test equation, confirm the opening and closing symbols are the same height, and confirm no stray period or missing bracket appears where you used an invisible delimiter.
Troubleshooting
- Braces do not appear. You typed
{ }instead of\{ \}. - Error with a single bracket after \left.
\leftand\rightmust come as a pair; use\right.or\left.for the side you want invisible (Overleaf). - Error in align, align* or aligned. A
\leftand its\rightsit on different lines or on opposite sides of&; balance them on each line as shown above. - Brackets larger or smaller than you want. Replace the automatic pair with a manual size such as
\Bigland\Bigr.
Where these commands are supported
| Tool | What the official page says | Source |
|---|---|---|
| KaTeX (browser math renderer) | Its supported-functions list names \left, \right, \middle, \big, \Big, \bigg, \Bigg (with l, m, r variants) under delimiter sizing, and lists \{ \} as well as \lbrace \rbrace |
katex.org/docs/supported.html, read 2026-11-08 |
| mathtools (LaTeX package) | Enhances documents with heavy mathematics and is built on amsmath; version 1.31 (2024-10-04), LPPL 1.3c, included in TeX Live and MiKTeX | ctan.org/pkg/mathtools, read 2026-11-08 |
For web pages that render LaTeX, see MathJax and LaTeX. Where a renderer differs from full LaTeX, test your delimiters in that renderer before publishing.
Free alternatives
| Option | Type | Official link |
|---|---|---|
| Overleaf | Online LaTeX editor (a free plan is offered; see the site for current limits) | overleaf.com |
| TeX Live | Free, open local LaTeX distribution | tug.org/texlive |
| MiKTeX | Free local LaTeX distribution | miktex.org |
| KaTeX | Open-source JavaScript library that renders LaTeX-style math in web pages (supports a subset of commands) | katex.org supported functions |
FAQ
Are () brackets or parentheses?
The round symbols () are parentheses (also called round brackets); [] are square brackets and {} are curly brackets or braces. Overleaf lists all three, plus angle brackets and pipes, as basic math-mode delimiters.
When to use [] vs ()?
LaTeX treats them identically apart from the symbol; the choice is a matter of notation in your field, such as marking interval ends. Follow your journal or discipline convention.
How to get {} to show in LaTeX?
Escape each brace with a backslash: \{ and \}. Unescaped braces are grouping characters and are not printed.
How do I type the parentheses?
Type ( and ) directly in math mode. For a bracket that grows with a fraction or other tall content, write \left( … \right).
How do I put parentheses around a fraction?
Use \left( \frac{a}{b} \right) so the parentheses scale to the fraction, as in the Overleaf example F = G \left( \frac{m_1 m_2}{r^2} \right).
How do I make big parentheses?
Either use \left and \right for automatic sizing, or one of \big, \Big, \bigg, \Bigg with an l or r (for example \Bigl( … \Bigr)) for a fixed size.
Sources
- Overleaf, “Brackets and Parentheses”, overleaf.com/learn/latex/Brackets_and_Parentheses, read 2026-11-08.
- KaTeX, “Supported Functions”, katex.org/docs/supported.html, read 2026-11-08.
- CTAN, mathtools package page, ctan.org/pkg/mathtools, read 2026-11-08.
