See parenthesis for an account of the rhetorical concept from which the name of the punctuation mark is derived.

In writing

Brackets are punctuation marks, used in pairs to set apart or interject text within other text. Types of brackets include parentheses ( ), (the singular is parenthesis) square brackets [ ], braces { }, and angle brackets 〈 〉. All these forms may be used according to typographical conventions that may vary from publication to publication and may vary even more from language to language. Some typical uses in English texts follow. Punctuation marks are written symbols that do not correspond to either phonemes (sounds) of a spoken language nor to lexemes (words and phrases) of a written language, but which serve to organize or clarify written language. ... Typographic work Typography (from the Greek words typos = form and grapho = write) is the art and technique of selecting and arranging type styles, point sizes, line lengths, line leading, character spacing, and word spacing for typeset applications. ...

Types of brackets

Parentheses ( )

Parentheses are used to contain parenthetical (or optional, additional) material in a sentence that could be removed without destroying the meaning of the main text. For example, "George Washington (the father of his country) was not the wooden figure with wooden teeth that many think him". Indeed, such an interjection is called a parenthesis, and may also be set off with dashes or commas. Overuse of parentheses is usually a sign of a badly structured text. For the round brackets used in punctuation, often called parentheses, see bracket. ... A dash is a punctuation mark, and is not to be confused with the hyphen, which has quite different uses. ... A comma ( , ) is a punctuation mark. ...

Parentheses may be used to add supplementary information, such as "Sen. Kennedy (D., Massachusetts) spoke at length".

Historically, parentheses have been used in place of the slash in order to depict alternatives, such as "parenthesis)(parentheses". A solidus, oblique or slash, /, is a punctuation mark. ...

Parentheses may also be nested (with one set inside another set (this is not commonly used in formal writing)). Sometimes square brackets will be used for the inner set of parentheses (in other words, a secondary phrase in parentheses).

Any punctuation inside parentheses or other brackets is independent from the rest of the text: "Mrs. Pennyfarthing (What? Yes, that was her name!) was my landlady".

In mathematics, parentheses are used to signify a different precedence of operators. For example, 2 + 3 × 4 would be 14, since the multiplication is done before the addition. (2 + 3) × 4 is 20, because the parentheses override normal precedence, causing the addition to be done first. They are also used to set apart the arguments to mathematical functions. For example, f(x) is the function f applied to the variable x. In the coordinate system, parentheses are used to denote a set of coordinates. For example, (4,7) represents the point located at 4 on the x-axis and 7 on the y-axis. History Main article: History of mathematics In addition to recognizing how to count concrete objects, prehistoric peoples also recognized how to count abstract quantities, like time -- days, seasons, years. ... A parameter is a measurement or value on which something else depends. ... In mathematics, a function is a relation, such that each element of a set (the domain) is associated with a unique element of another (possibly the same) set (the codomain, not to be confused with the range). ... In computer science and mathematics, a variable is a symbol denoting a quantity or symbolic representation. ... See Cartesian coordinate system or Coordinates (elementary mathematics) for a more elementary introduction to this topic. ...

Parentheses are sometimes called round brackets, curved brackets or, colloquially, parens, or fingernails. John Lennard (in "The exploitation of parentheses in English printed verse") usefully coined the term lunula to refer specifically to the opening curved bracket, the closing curved bracket and the textual contents between.

Square brackets [ ]

Square brackets are used to enclose explanatory or missing [...] material, especially in quoted text. For example, "I appreciate it [the honor], but I must refuse". Or, "the future of psionics [See definition] is in doubt". Parapsychology is the study of the evidence involving phenomena where a person seems to affect or gain information about something through a means not currently explainable within the framework of mainstream, conventional science. ...

The bracketed expression [sic] (Latin for "thus") is used to indicate errors that are "thus in the original"; a bracketed ellipsis [...] is used to indicate deleted material; bracketed comments are used to indicate when original text has been modified for clarity: "I'd like to thank [several unimportant people] and my parentals [sic] for their love, tolerance [...] and assistance [italics added]".

Square brackets are also sometimes used as parentheses within parentheses - "secondary parentheses" as mentioned earlier.

With the International Phonetic Alphabet, square brackets are used to indicate a phonetic transcription (as opposed to a phonemic one). The International Phonetic Alphabet is a phonetic alphabet used by linguists to accurately and uniquely represent each of the wide variety of sounds (phones or phonemes) the human vocal apparatus can produce. ... Phonetic ™ (pho-NET-ic) is a nationwide voicemail-to-text messaging service available for most digital mobile phones in which a subscriber is provided a special voice mailbox for the purpose of converting all incoming voice messages into actual text for reading via short messaging (also known as SMS, text... In spoken language, a phoneme is a basic, theoretical unit of sound that can distinguish words (i. ...

In chemistry, square brackets can also be used to represent the concentration of a chemical substance, or to denote a complex ion. Chemistry (in Greek: χημεία) is the science of matter and its interactions with energy and itself (see physics, biology). ... Concentration is a very common concept used in chemistry and related fields. ... A chemical substance is any material substance used in or obtained by a process in chemistry: A chemical compound is a substance consisting of two or more chemical elements that are chemically combined in fixed proportions. ... complex In chemistry, a complex is a structure composed of a central metal atom or ion, generally a cation, surrounded by a number of negatively charged ions or neutral molecules possessing lone pairs. ...

In wikis like Wikipedia, double square brackets ( [[ ]] ) are used to form wiki links to other pages. A Wiki or wiki (pronounced , or ; see Pronunciation below) is a web application that allows users to add content, as on an Internet forum, but also allows anyone to edit the content. ... Wikipedia is a Web-based, free-content encyclopedia that is written collaboratively by volunteers. ... Note: while the definitions below may be useful for understanding and writing text in the community pages (Talk, Wikipedia, User, Meta, etc. ...

Curly brackets or braces { }

Curly brackets (so-called in European English; North American English prefers braces) are sometimes used in prose to indicate a series of equal choices: "Select your animal {goat, sheep, cow, horse} and follow me". They are used in specialized ways in poetry and music (to mark repeats or joined lines). In mathematics they are used to delimit sets. History Main article: History of mathematics In addition to recognizing how to count concrete objects, prehistoric peoples also recognized how to count abstract quantities, like time -- days, seasons, years. ... The notion of a set is one of the most important and fundamental concepts in modern mathematics. ...

Presumably due to the similarity of the words brace and bracket (they share an etymology), many people casually treat brace as a synonym for bracket. Therefore, when it is necessary to avoid any possibility of confusion, such as in computer programming, it may be best to use the term curly bracket rather than brace. However, general usage in North American English favors the latter form. The term curly braces is redundant since that is the only kind of braces there are. Etymology is the study of the origins of words. ... Synonyms (in ancient Greek syn συν = plus and onoma όνομα = name) are different words with similar or identical meanings. ...

In computer programming, curly brackets sometimes denote the beginning and ending of a sequence of statements. Computer programming (often simply programming) is the craft of implementing one or more interrelated abstract algorithms using a particular programming language to produce a concrete computer program. ...

Angle brackets or Chevrons 〈 〉

Angle brackets (〈, 〉) are often used to enclose highlighted material. Some dictionaries use angle brackets to enclose short excerpts illustrating the usage of words. True angle brackets are not available on a typical computer keyboard, so the "less than" and "greater than" symbols are used instead (<, >). These are often loosely referred to as angle brackets when used in this way. For example, the symbols < and > are often used to set apart URLs in text, such as "I found it in Wikipedia <http://www.wikipedia.org/>". A Uniform Resource Locator, URL (either pronounced as earl (IPA: [ɜː˞l]; SAMPA: [3:`l]) or spelled out), or Web address, is a standardized address for some resource (such as a document or image) on the Internet (or elsewhere). ...

Angle brackets are used in mathematics and logic to delimit ordered n-tuples. In mathematics, a tuple is a finite sequence of objects (a list of a limited number of objects). ...

Single and double angle brackets (〈〈, 〉〉) or pairs of the appropriate comparison operators (<<, >>) are sometimes used instead of guillemets when the proper glyphs are not available. Quotation marks, also called quotes or inverted commas, are punctuation marks used in pairs to set off speech, a quotation, or a phrase. ... A glyph is a carved figure or character, incised or in relief; a carved pictograph; hence, a pictograph representing a form originally adopted for sculpture, whether carved or painted. ...

The mathematical or logical symbols for greater-than (>) and less-than (<), when used as such, are not punctuation marks.

In computing

• Opening and closing parentheses correspond to Unicode and ASCII characters 40 and 41, or 0x0028 and 0x0029, respectively.
• For square brackets corresponding values are 91 and 93, or 0x005B and 0x005D.
• For braces, 123 and 125, or 0x007B and 0x007D.
• True angle brackets are available in Unicode at code points 9001 and 9002, or 0x2329 and 0x232A. The less than and greater than symbols can be found in both Unicode and ASCII at code points 60 and 62 respectively, or 0x003C and 0x003E.

Also, in many computer languages: In computing, Unicode is the international standard whose goal is to provide the means to encode the text of every document people want to store in computers. ... There are 95 printable ASCII characters, numbered 32 to 126. ... In mathematics and computer science, hexadecimal or simply hex is a numeral system with a radix or base of 16 usually written using the symbols 0–9 and A–F or a–f. ... A computer language is a language used by, or in association with, computers. ...

• "(" and ")" are used to contain the arguments to functions: substring($val,10,1). Parentheses are so ubiquitous in the Lisp programming language that the name is said to be an acronym for "Lots of Irritating Superfluous Parentheses". They may also be used to indicate the start and end of lists.
• "[" and "]" are used to define the number of elements in an array, or reference one of those elements: $queue[3]. In MediaWiki's syntax, a double square-bracket set is used to make a wikilink to the term defined inside: [[Bracket]].
• "{" and "}" are used to define the beginning and ending of blocks of code or define the initial contents of an array. To complicate things, in the Pascal programming language, "{" and "}" define the beginning and ending of comments. Languages which use the former convention are said to belong to the Curly brace family.
• "<" and ">" are used in SGML (and other formats based on SGML, such as HTML and XML), to enclose code tags: <div>.

Lisp is a functional programming language family with a long history. ... MediaWiki is a Wiki software package licensed under the GNU General Public License. ... Pascal is one of the landmark computer programming languages on which generations of students cut their teeth and variants of which are still widely used today. ... This article describes the syntax of programming languages. ... The Standard Generalized Markup Language (SGML) is a metalanguage in which one can define markup languages for documents. ... In computing, HyperText Markup Language (HTML) is a markup language designed for the creation of web pages and other information viewable in a browser. ... The Extensible Markup Language (XML) is a W3C-recommended general-purpose markup language for creating special-purpose markup languages. ...

Layout rules

In normal text an opening bracket is not put at the end of a line, and a closing bracket not at the beginning. However, in computer code this is often done to aid readability. For example, a bracketed list of items separated by semi-colons may be written with the brackets on separate lines, and the items, followed by the semicolon, each on one line.

For example

 H1 { font-weight: bold; font-size: 12pt; line-height: 14pt } 

may also be written

 H1 { font-weight: bold; font-size: 12pt; line-height: 14pt } 

A superfluous semicolon may be added after the last item for uniformity of the item lines.

See: Indent style Indent style describes how different programmers indent blocks of code to convey the programs structure. ...

In mathematics

In addition to the use of parentheses to specify the order of operations, both parentheses and square brackets can also be used to denote an interval. The notation [a, c) is used to indicate a sequence from a to c that is inclusive of a but exclusive of c. That is, [5, 12) would be the set of all real numbers between 5 and 12, including 5 but except 12. The numbers may come as close as they like to 12, including 11.999 and so forth (with any finite number of 9s), but 12.0 is not included. :) internet use mostly in e-mail and Instant Messenger (IM) programs - smilie face used to show happiness, a happy responce, a smile. ... In arithmetic and elementary algebra, certain rules are used for the order in which the operations in algebraic expressions are to be evaluated. ... In elementary algebra, an interval is a set that contains every real number between two indicated numbers, and possibly the two numbers themselves. ... In mathematics, a set is called finite if and only if there is a bijection between the set and some set of the form {1, 2, ..., n} where is a natural number. ...

The endpoint adjoining the square bracket is known as closed, while the endpoint adjoining the parenthesis is known as open. If both types of brackets are the same, the entire interval may be referred to as closed or open as appropriate. Whenever infinity or negative infinity is used as an endpoint, it is always considered open and adjoined to a parenthesis. Infinity has discrete meanings in mathematics, philosophy, theology and everyday life. ...

This is used in mathematical notation, and appears in some computer programming languages. See the article Interval (mathematics) for a more complete treatment of the subject. History Main article: History of mathematics In addition to recognizing how to count concrete objects, prehistoric peoples also recognized how to count abstract quantities, like time -- days, seasons, years. ... In elementary algebra, an interval is a set that contains every real number between two indicated numbers, and possibly the two numbers themselves. ...

In quantum mechanics, brackets are also used as part of Dirac's formalism to note vectors form the dual spaces of the Bra <A| and the Ket |B>.

In sports

• Tournament brackets, such as those used in sports tournaments (tennis tournaments, 9-ball tournaments, or March Madness and other NCAA tournaments).

In tournaments, bracket is commonly used to refer to the diagrammatic representation of the series of games played during the tournament. ... A tournament is an organized competition in which many participants play each other in individual games. ... Tennis is a racquet sport played between either two players (singles) or two teams of two players (doubles). Player(s) use a stringed racquet to strike a hollow rubber ball over a net into the opponents court. ... Nine ball is a billiards game played with a cue ball and 9 colored object balls, numbered 1 through 9. ... March Madness is a popular colloquial term for the process of deciding the annual champion of NCAA collegiate basketball in the United States. ... The National Collegiate Athletic Association (NCAA, often said NC-Double-A) is a voluntary association of about 1200 institutions, conferences, organizations and individuals that organizes the athletics programs of many colleges and universities in the United States. ...

In mechanics and structures

A bracket may be an inverted "L" shape, such as is usually used to hold up a shelf, or a rafter extension and its diagonal brace supporting an overhanging roof over a gable. Decorative brackets used in furniture and mantlepieces are called corbels. In Medieval architecture a corbel or console names a piece of stone jutting out of a wall to carry any superincumbent weight. ...

Reference

Turnbull et al., The Graphics of Communication, Holt, New York: 1964 states that what are depicted as square brackets above are called braces and curly brackets are called brackets. This was the terminology in US printing prior to computers.

See also

• tax bracket
• bra-ket notation
• Emoticon