Bracket
Brackets are punctuation marks used in pairs to set apart or interject text within other text. With respect to computer science, the term refers to only the square or box type.
Types of brackets include parentheses or round brackets , box brackets or square brackets [ ], curly brackets or 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.
Encyclopedia
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Brackets are punctuation marks used in pairs to set apart or interject text within other text. With respect to computer science, the term refers to only the square or box type.
Types of brackets include
parentheses or
round brackets ,
box brackets or
square brackets [ ],
curly brackets or
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.
Usage
In addition to referring to the class of all types of brackets, the unqualified word
bracket is most commonly used to refer to a specific type of bracket. In modern American usage, this is usually the square bracket, whereas in modern British usage it is usually the parenthesis.
In fact, in American usage, parentheses are usually considered separately from other brackets, and calling them
brackets at all is unusual, even though they serve a similar function.
Types of brackets
Parentheses
Parentheses – sometimes called
round brackets,
curved brackets or just
brackets; or, colloquially,
parens, or
fingernails – are used to contain parenthetical material in a sentence that could be removed without destroying the meaning of the main text.
John Lennard usefully coined the term
lunula to refer specifically to the opening curved bracket, the closing curved bracket and the textual contents between.
In formal writing, parentheses may be used to add supplementary information, such as "Sen. Kennedy spoke at length."
In literature and informal writing, parenthetical phrases have been used extensively in stream of consciousness literature. Of particular note is the great southern American author
William Faulkner, whose use of parenthetical constructions was legendary, effective, and frustrating. See
Absalom, Absalom and the Quentin section of
The Sound and the Fury for the best known examples. In most writing, overuse of parentheses is usually a sign of a badly structured text.
Historically, parentheses have been used where the solidus is modernly used—that is, in order to depict alternatives, such as "parenthesis) is used to indicate an interval 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 , but 12.0 is not included. In Europe, the notation
[5,12[ is also used for this.
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.
This is used in mathematical notation, and appears in some computer programming languages. See the article Interval for a more complete treatment of the subject.
In quantum mechanics, angle brackets are also used as part of
Dirac's formalism, bra-ket notation, to note vectors from the dual spaces of the Bra A| and the Ket |B. In statistical mechanics, angle brackets denote ensemble or time average.
In group theory and ring theory, square brackets are used to denote the commutator. In group theory, the commutator
[g,
h] is commonly defined as
g−1h−1gh. In ring theory, the commutator
[a,
b] is defined as
ab −
ba. Furthermore, in ring theory, braces are used to denote the anticommutator where is defined as
ab +
ba.
Various notations, like the vinculum have a similar effect to brackets in specifying order of operations, or otherwise grouping several characters together for a common purpose.
In the Z formal specification language, curly braces define a set and angle brackets define a sequence.
In sports
In law
Brackets are used in the citation of
law reports to identify whether the report series is sorted by volume number - in which case round brackets are used - or by year - in which case square brackets are used. For example: 158 CLR 1 or [1998] 2 All ER 153.
In mechanics and structures
A bracket is a type of a structural support. It 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 mantelpieces are called
corbels.
In structural and mechanical engineering the term
bracket may have a synonomous meaning to brace, angle brace, angle iron, angle piece, and
buttress.
Reference
See also
- Tax bracket
- Bra-ket notation
- Bracket notation, a text-based method of tracking changes to a document
- Emoticon
- Japanese typographic symbols
