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A bracket is either of two tall fore- or back-facing punctuation marks commonly used to isolate a segment of text or data from its surroundings. They come in four main pairs of shapes, as given in the box to the right, which also gives their names, that vary between British English and American English. "Brackets", without further qualification, are in British English the ... marks and in American English the ... marks.
Other symbols are repurposed as brackets in specialist contexts, such as those used by linguists.
Brackets are typically deployed in symmetric pairs, and an individual bracket may be identified as a "left" or "right" bracket or, alternatively, an "opening bracket" or "closing bracket", respectively, depending on the directionality of the context.
In casual writing and in technical fields such as computing or linguistic analysis of grammar, brackets nest, with segments of bracketed material containing embedded within them other further bracketed sub-segments. The number of opening brackets matches the number of closing brackets in such cases.
Various forms of brackets are used in mathematics, with specific mathematical meanings, often for denoting specific mathematical functions and .
Most typewriters only had the left and right parentheses. Square brackets appeared with some teleprinters.
Braces (curly brackets) first became part of a character set with the 8-bit code of the IBM 7030 Stretch.
In 1961, ASCII contained parentheses, square, and curly brackets, and also less-than and greater-than signs that could be used as angle brackets.
In formal writing, "parentheses" is also used in British English.
A comma before or after the material can also be used, though if the sentence contains commas for other purposes, visual confusion may result. A dash before and after the material is also sometimes used.
Parentheses may be used in formal writing to add supplementary information, such as "Senator John McCain (R - Arizona) spoke at length". They can also indicate shorthand for "Uncertain plural" for nouns, e.g. "the claim(s)". It can also be used for gender-neutral language, especially in languages with grammatical gender, e.g. "(s)he agreed with his/her physician" (the slash in the second instance, as one alternative is replacing the other, not adding to it).
Parenthetical phrases have been used extensively in informal writing and stream of consciousness literature. Examples include the southern American author William Faulkner (see Absalom, Absalom! and ) as well as poet E. E. Cummings.
Parentheses have historically been used where the em dash is currently used in alternatives, such as "parenthesis)(parentheses". Examples of this usage can be seen in editions of Fowler's Dictionary of Modern English Usage.
Parentheses may be nested (generally with one set (such as this) inside another set). This is not commonly used in formal writing (though sometimes other brackets especially will be used for one or more inner set of parentheses in).
In phonetics, parentheses are used for indistinguishableIPA Handbook p. 175 or unidentified utterances. They are also seen for silent articulation (mouthing),IPA Handbook p. 191 where the expected phonetic transcription is derived from lip-reading, and with periods to indicate silent pauses, for example or .
In Mathematica and the Wolfram language, parentheses are used to indicate groupingfor example, with pure anonymous functions.
This is a notation that was pioneered by Berzelius, who wanted chemical formulae to more resemble algebraic notation, with brackets enclosing groups that could be multiplied (e.g. in 3(AlO2 + 2SO3) the 3 multiplies everything within the parentheses).
In chemical nomenclature, parentheses are used to distinguish structural features and multipliers for clarity, for example in the polymer poly(methyl methacrylate).
and are ''square brackets'' in both British and American English, but are also more simply ''brackets'' in the latter.
An older name for these brackets is "crotchets".Smith, John. The Printer's Grammar p. 84.
When quoted material is in any way altered, the alterations are enclosed in square brackets within the quotation to show that the quotation is not exactly as given, or to add an annotation. For example: The Plaintiff asserted his cause is just, stating,
In the original quoted sentence, the word "my" was capitalized: it has been modified in the quotation given and the change signalled with brackets. Similarly, where the quotation contained a grammatical error (is/are), the quoting author signalled that the error was in the original with " sic" (Latin for 'thus').
A bracketed ellipsis, ..., is often used to indicate omitted material: "I'd like to thank several for their tolerance ..." Bracketed comments inserted into a quote indicate where the original has been modified for clarity: "I appreciate it the, but I must refuse", and "the future of psionics see is in doubt". Or one can quote the original statement "I hate to do laundry" with a (sometimes grammatical) modification inserted: He "hates to do laundry".
Additionally, a small letter can be replaced by a capital one, when the beginning of the original printed text is being quoted in another piece of text or when the original text has been omitted for succinctness— for example, when referring to a original: "To the extent that policymakers and elite opinion in general have made use of economic analysis at all, they have, as the saying goes, done so the way a drunkard uses a lamppost: for support, not illumination", can be quoted succinctly as: "Policymakers ... have made use of economic analysis ... the way a drunkard uses a lamppost: for support, not illumination." When nested parentheses are needed, brackets are sometimes used as a substitute for the inner pair of parentheses within the outer pair. When deeper levels of nesting are needed, convention is to alternate between parentheses and brackets at each level.
Alternatively, empty square brackets can also indicate omitted material, usually single letter only. The original, "Reading is also a process and it also changes you." can be rewritten in a quote as: It has been suggested that reading can "also change you".
In translated works, brackets are used to signify the same word or phrase in the original language to avoid ambiguity. For example: He is trained in the way of the open hand karate.
Style guide originating in the news industry of the twentieth century, such as the AP Stylebook, recommend against the use of square brackets because "They cannot be transmitted over news wires." However, this guidance has little relevance outside of the technological constraints of the industry and era.
In linguistics, phonetic transcriptions are generally enclosed within square brackets, whereas phonemic transcriptions typically use paired slashes, according to International Phonetic Alphabet rules. Pipes (| |) are often used to indicate a Morphophoneme rather than phonemic representation. Other conventions are double slashes (⫽ ⫽), double pipes (‖ ‖) and curly brackets ({ }).
In lexicography, square brackets usually surround the section of a dictionary entry which contains the etymology of the word the entry defines.
Square brackets are used to denote parts of the text that need to be checked when preparing drafts prior to finalizing a document.
In some other countries (such as England and Wales), square brackets are used to indicate that the year is part of the citation and parentheses are used to indicate the year the judgment was given. For example:
This case is in the 1954 volume of the Appeal Cases reports, although the decision may have been given in 1953 or earlier. Compare with:
This citation reports a decision from 1954, in volume 98 of the Solicitors Journal which may be published in 1955 or later.
They often denote points that have not yet been agreed to in legal drafts and the year in which a report was made for certain case law decisions.
Square brackets may be used exclusively or in combination with parentheses to represent intervals as interval notation. For example, represents the set of real numbers from 0 to 5 inclusive. Both parentheses and brackets are used to denote a half-open interval; would be the set of all real numbers between 5 and 12, including 5 but not 12. The numbers may come as close as they like to 12, including 11.999 and so forth, but 12.0 is not included. In some European countries, the notation is also used. The endpoint adjoining the square bracket is known as closed, whereas the endpoint adjoining the parenthesis is known as open.
In group theory and ring theory, brackets denote the commutator. In group theory, the commutator is commonly defined as . In ring theory, the commutator is defined as .
The brackets stand for a function that maps a linguistic expression to its "denotation" or semantic value. In mathematics, double brackets may also be used to denote intervals of integers or, less often, the floor function. In papyrology, following the Leiden Conventions, they are used to enclose text that has been deleted in antiquity.
Half brackets are used in English to mark added text, such as in translations: "Bill saw ⸤her⸥".
In editions of papyrology texts, half brackets, ⸤ and ⸥ or ⸢ and ⸣, enclose text which is lacking in the papyrus due to damage, but can be restored by virtue of another source, such as an ancient quotation of the text transmitted by the papyrus.M.L. West (1973) Textual Criticism and Editorial Technique (Stuttgart) 81. For example, Callimachus Iambus 1.2 reads: ἐκ τῶν ὅκου βοῦν κολλύ⸤βου π⸥ιπρήσκουσιν. A hole in the papyrus has obliterated βου π, but these letters are supplied by an ancient commentary on the poem. Second intermittent sources can be between ⸢ and ⸣. Quine corners are sometimes used instead of half brackets.
and are ''curly brackets'' or ''braces'' in both American and British English.
Braces used to be used to connect multiple lines of poetry, such as triplets in a poem of rhyming , although this usage had gone out of fashion by the 19th century.
Another older use in prose was to eliminate duplication in lists and tables. Two examples here from Charles Hutton's 19th century table of weights and measures in his A Course of Mathematics:
+ In this kingdom Length is a Yard. Surface is a Square Yard, the of an Acre. ⎰ Solidity is a Cubic Yard. ⎱ Capacity is a Gallon. Weight is a Pound.
+ Imperial measure of CAPACITY for coals, culm, lime, fish, potatoes, fruit,– and other goods commonly sold by heaped measure: ⎱ Cubic Inches, nearly ⎰ ⎱ Cubic Feet, nearly ⎰
As an extension to the International Phonetic Alphabet (IPA), braces are used for prosodic notation.
In various , they enclose a group of strings that are used in a process known as brace expansion, where each successive string in the group is interpolated at that point in the command line to generate the command-line's final form. The mechanism originated in the C shell and the string generation mechanism is a simple interpolation that can occur anywhere in a command line and takes no account of existing filenames.
In they are used for repetition, such as in extended Backus–Naur form.
In the Z notation formal specification language, braces define a set.
They are often also used to denote the Poisson bracket between two quantities.
In ring theory, braces denote the anticommutator where is defined as .
Strictly speaking they are distinct from V-shaped chevrons, as they have (where the typography permits it) a broader span than chevrons, although when printed often no visual distinction is made.
The ASCII less-than and greater-than characters and are often used for angle brackets. In many cases, only those characters are accepted by computer programs, and the Unicode angle brackets are not recognized (for instance, in ). The characters for "single" ( and ) are also often used, and sometimes normal guillemets ( and ) when nested angle brackets are needed.
The angle brackets or chevrons and are for mathematical use and Western languages, whereas and are for East Asian languages. The chevrons at U+2329 and U+232A are deprecated in favour of the U+3008 and U+3009 East Asian angle brackets. Unicode discourages their use for mathematics and in Western texts, because they are canonically equivalent to the CJK code points U+300n and thus likely to render as double-width symbols. The less-than and greater-than symbols are often used as replacements for chevrons.
In textual criticism, and hence in many editions of pre-modern works, chevrons denote sections of the text which are illegible or otherwise lost; the editor will often insert their own reconstruction where possible within them. (2025). 9781579582180, Edinburgh University Press. ISBN 9781579582180
In , chevrons are often used to mark dialogue that has been translated notionally from another language; in other words, if a character is speaking another language, instead of writing in the other language and providing a translation, one writes the translated text within chevrons. Since no foreign language is actually written, this is only notionally translated.
In linguistics, angle brackets identify (, letters of an alphabet) or orthography, as in "The English word is spelled ."
In epigraphy, they may be used for mechanical transliterations of a text into the Latin script.
In East Asian punctuation, angle brackets are used as . Chevron-like symbols are part of standard Chinese language, Japanese and less frequently Korean language punctuation, where they generally enclose the titles of books, as: 〈 ︙ 〉 or 《 ︙ 》 for traditional tategaki — written in vertical lines — and as 〈 ... 〉 or 《 ... 》 for yokogaki printing — in horizontal.
In mathematical physics, especially quantum mechanics, it is common to write the inner product between elements as , as a short version of , or , where is an operator. This is known as Dirac notation or bra–ket notation, to note vectors from the of the Bra . But there are other notations used.
In continuum mechanics, chevrons may be used as Macaulay brackets.
In the Z notation formal specification language, angle brackets define a sequence.
In HTML, angle brackets (actually 'greater than' and 'less than' symbols) are used to bracket meta text. For example denotes that the following text should be displayed as bold. Pairs of meta text tags are required – much as brackets themselves are usually in pairs. The end of the bold text segment would be indicated by . This use is sometimes extended as an informal mechanism for communicating mood or tone in digital formats such as messaging, for example adding "<sighs>" at the end of a sentence.
| +Unicode and HTML encodings for various bracket characters | ||
| quasi-quotation | ⌜ quasi-quotation⌝ ⌜ editorial notation⌝ | |
| ⌞ editorial notation⌟ | ||
| Brackets with quill | ⁅...⁆ | |
| Fullwidth parentheses | ｟...｠ | |
| Technical/mathematical (specialized) | ⎸boxed text⎹ | |
| ⏠ tortoise shell brackets ⏡ | ||
| ⟅...⟆ | ||
| ⟓pullback...pushout⟔ | ||
| ⟦...⟧ | ||
| ⟬white tortoise shell brackets⟭ | ||
| ⦇⦈ | ||
| ⦉⦊ | ||
| ⦓inequality sign brackets⦔ | ||
| ⦕inequality sign brackets⦖ | ||
| ⦗black tortoise shell brackets⦘ | ||
| ⧘...⧙ | ||
| ⧚...⧛ | ||
| 〚...〛 | ||
| Half brackets | ⸢ editorial notation⸣ | |
| ⸤ editorial notation⸥ | ||
| Compatibility variants for CNS 11643 | ﹙...﹚ | |
| ﹛...﹜ | ||
| ﹝...﹞ | ||
| ❲light tortoise shell bracket ornament❳ | ||
| N'Ko | ||
| Ogham | ᚛ᚑᚌᚐᚋ᚜ | |
| ⹂ | ||
| Tibetan alphabet | ༺དབུ་ཅན་༻ | |
| ༼༡༢༣༽ | ||
| New Testament editorial marks | ⸂...⸃ | |
| ⸄...⸅ | ||
| ⸉...⸊ | ||
| ⸌...⸍ | ||
| Medieval studies | ⸦crux⸧ | |
| Indicate ellipsis in certain conventions for Japanese transliteration | ⹕optional ellipsis⹖ | |
| ⹗obligatory ellipsis⹘ | ||
| Quotation (East-Asian texts) | 〔...〕 | |
| 〖...〗 | ||
| 〘...〙 | ||
| 〝...〞 | ||
| Quotation (halfwidth East-Asian texts) | ｢ｶﾀｶﾅ｣ | |
| Quotation (fullwidth East-Asian texts) | 「表題」 | |
| 『表題』 | ||
| 【表題】 | ||
| Vertical bracket presentation forms | ︗︙︙︘ | |
| ︵︙︙︶ | ||
| ︷︙︙︸ | ||
| ︹︙︙︺ | ||
| ︻︙︙︼ | ||
| ︽︙︙︾ | ||
| ︿︙︙﹀ | ||
| ﹁︙︙﹂ | ||
| ﹃︙︙﹄ | ||
| ﹇︙︙﹈ | ||
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