Bracket
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 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 subformulas.
History
Angle brackets or chevrons ⟨ ⟩ were the earliest type of bracket to appear in written English. Erasmus coined the term lunula to refer to the round brackets or parentheses recalling the shape of the crescent moon.Most typewriters only had the left and right parentheses. Square brackets appeared with some teleprinters.
Braces 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.
Typography
In English, typographers mostly prefer not to set brackets in italics, even when the enclosed text is italic. However, in other languages like German, if brackets enclose text in italics, they are usually also set in italics.Parentheses or round brackets
The marks and are parentheses in American English, and either round brackets or simply brackets in British English.In formal writing, "parentheses" is also used in British English.
Uses of ( )
Parentheses contain adjunctive material that serves to clarify or is aside from the main point.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 spoke at length". They can also indicate shorthand for "either singular or plural" for nouns, e.g. "the claim". It can also be used for gender-neutral language, especially in languages with grammatical gender, e.g. "he agreed with his/her physician".
Parenthetical phrases have been used extensively in informal writing and stream of consciousness literature. Examples include the southern American author William Faulkner as well as poet E. E. Cummings.
Parentheses have historically been used where the em dash is currently used in alternatives, such as "parenthesis).
Language
A parenthesis in rhetoric and linguistics refers to the entire bracketed text, not just to the enclosing marks used. Taking as an example the sentence "Mrs. Pennyfarthing was my landlady.", the explanatory phrase between the parentheses is itself called a parenthesis. Again, the parenthesis implies that the meaning and flow of the bracketed phrase is supplemental to the rest of the text and the whole would be unchanged were the parenthesised sentences removed. The term refers to the syntax rather than the enclosure method: the same clause in the form "Mrs. PennyfarthingWhat? Yes, that was her name!was my landlady" is also a parenthesis.In phonetics, parentheses are used for indistinguishable or unidentified utterances. They are also seen for silent articulation, where the expected phonetic transcription is derived from lip-reading, and with periods to indicate silent pauses, for example or.
In some languages, such as the Nicodemus orthography for Coeur d’Alene, parentheses are used as phonemic symbols instead of punctuation.
Enumerations
An unpaired right parenthesis is often used as part of a label in an ordered list, such as this one:Accounting
Traditionally in accounting, contra amounts are placed in parentheses. A debit balance account in a series of credit balances will have parentheses and vice versa.Parentheses in mathematics
Parentheses are used in mathematical notation to indicate grouping, often inducing a different order of operations. For example: in the usual order of algebraic operations, equals 14, since the multiplication is done before the addition. However, equals 20, because the parentheses override normal precedence, causing the addition to be done first. Some authors follow the convention in mathematical equations that, when parentheses have one level of nesting, the inner pair are parentheses and the outer pair are square brackets. Example:Parentheses in programming languages
Parentheses are included in the syntaxes of many programming languages. Typically needed to denote an argument; to tell the compiler what data type the method/function needs to look for first in order to initialise. In some cases, such as in LISP, parentheses are a fundamental construct of the language. They are also often used for scoping functions and operators and for arrays. In syntax diagrams they are used for grouping, such as in extended Backus–Naur form.In Mathematica and the Wolfram language, parentheses are used to indicate groupingfor example, with pure anonymous functions.
Taxonomy
If it is desired to include the subgenus when giving the scientific name of an animal species or subspecies, the subgenus's name is provided in parentheses between the genus name and the specific epithet. For instance, Polyphylla ''alba is a way to cite the species Polyphylla alba while also mentioning that it is in the subgenus Xerasiobia. There is also a convention of citing a subgenus by enclosing it in parentheses after its genus, e.g., Polyphylla is a way to refer to the subgenus Xerasiobia within the genus Polyphylla. Parentheses are similarly used to cite a subgenus with the name of a prokaryotic species, although the International Code of Nomenclature of Prokaryotes requires the use of the abbreviation "subgen". as well, e.g., Acetobacter liquefaciens''.Chemistry
Parentheses are used in chemistry to denote a repeated substructure within a molecule, e.g. HC3 or, similarly, to indicate the stoichiometry of ionic compounds with such substructures: e.g. Ca2.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.
In chemical nomenclature, parentheses are used to distinguish structural features and multipliers for clarity, for example in the polymer poly.
Square brackets
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".
Uses of
Square brackets are often used to insert explanatory material or to mark where a passage was omitted from an original material by someone other than the original author, or to mark modifications in quotations. In transcribed interviews, sounds, responses and reactions that are not words but that can be described are set off in square brackets — "... ...".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 capitalised: it has been modified in the quotation given and the change signalled with brackets. Similarly, where the quotation contained a grammatical error, the quoting author signalled that the error was in the original with "".
A bracketed ellipsis, , is often used to indicate omitted material: "I'd like to thank for their tolerance "
Bracketed comments inserted into a quote indicate where the original has been modified for clarity: "I appreciate it , but I must refuse", and "the future of psionics is in doubt". Or one can quote the original statement "I hate to do laundry" with a modification inserted: He "hate 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 verbose 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: "olicymakers 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 .
Style and usage guides 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 morphophonemic 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.