Brackets, parentheses, and braces are typically used as delimiters in written natural languages, mathematical equations, programming languages, and other formal languages. A 101-key US keyboard has four types:

( )
Parentheses, Round Brackets1
[ ]
Square Brackets
< >
Angle Brackets
{ }
Braces, Curly Brackets1

Unfortunately, there is not a universally agreed upon name for the class of these characters. Many people I've talked to call them "brackets" because the word occurs in the name for two of the four delimiters. This is thwarted, however, by another group of people who call square brackets just "brackets" (thereby implying that they are a superclass of angle brackets). Even Computer Science has not adopted a standard name for the class (see "bracket matching" and "paren matching").

1: Alternative naming conventions supplied by Gritchka -- thanks!

Brackets are very commonly used in normal writing, and sometimes the writers aren't even aware they're doing it. For example, one of the above write-ups has a list
  • When All Else Fails (Fat Wreck Chords)
  • Novelty Forever (Fat Wreck Chords)
  • E is for Everything on FAT (Fat Wreck Chords)
in which the words "Fat Wreck Chords" are in brackets. Below that the band members are named, and their instruments (guitar) etc. are put in brackets, just as I have done.

The noder just above me put the words "thereby implying that they are a superclass of angle brackets" in brackets, indicating that those words were parenthetical to the main thought of the sentence. Often this use of bracketing is equivalent to using dashes around the clause. A part of a sentence in brackets (like this, for example) should be omissible without much damage to the meaning of what remains.

Brackets can also be called round brackets, because of their shape, to distinguish them from similar punctuation: square, curly, and angle brackets. Unlike normal brackets, square brackets are not much used in ordinary writing, but in more formal writing they enclose words omitted in the original but supplied to make sense; or where an alteration is necessary because of another omission. Curly and angle brackets are not used in normal text at all.

Printers use the technical term parentheses instead of brackets, and by brackets they mean square brackets. This usage is also prevalent in the United States; this may result in confusion in computing circles, since in that field the terminology tends to originate in the US.

A punch up the bracket is an old term for a punch up or on the jaw or perhaps nose or perhaps some other part.

Edmund Husserl in his philosophy of phenomenology used the Greek word epoche, which is sometimes translated as bracketing: a way of shutting off part of the world and concentrating on one knowable thing.

to bracket: in the context of photography, taking exactly the same shot with different exposure settings. It is a typical behavior of the professional or obsessive amateur photographer.
It is done when you are not absolutely sure of exposure (high contrast or unfamiliar setting), or when the picture must absolutely come out right. Bracketing is particularly advisable when shooting slide film and other stock that has little exposure latitude.

Some cameras can do the bracketing for you; this is called auto exposure bracketing or AEB.
see also: bracketing] in filmography, in yossarian's excellent Film Terms glossary.

Also written bra-ket. The product of a bra, <b|, with a ket, |a>, is written <b|a>. If you're working with vectors, it's the dot product of the bra and the ket. If you have more esoteric things, like wavefunctions, you just multiply them.

Brackets are useful for finding the probability that a measurement will yield a given result; the probability that a system in a given state X will be measured by an operator with eigenstate B is |<X|B>|2

In typography, a bracket is a curve that connects the serif to the stroke. Popular, well-designed, bracketed fonts include Times New Roman, Caslon, and Garamond.

        |        |                         |        |                 
        |        |                         |        |                 
        |        |                         |        |                 
        |        |                         |        |                 
        |        |                         |        |                 
       /          \                        |        |                 
 +----`            `-----+          +------+        +-------+
 +-----------------------+          +-----------------------+
        bracketed                         unbracketed

When creating typography in stone, softer metal, or wood, brackets help structurally strengthen and stabilize the serif. For this reason, all early fonts were bracketed.

Brackets and the fashion of kings
Back when royalty cared about such things, in 1692 Louis XIII asked his Imprimerie Royale to reconceive typography on engineering and scientific principles rather than “merely” artistic ones. Among the committee's stylistic decisions toward meeting this goal (and it took years and heated debates) was the reduction of the bracket. Their ideal font, the Romain du Roi, became the height of fashion but protected for use strictly in royal printing. In fact it was a capital offense to use it otherwise. So other print houses around France tried to copy the Romain du Roi with just enough changes to keep their heads attached. The designers noticed the reduced bracket and exaggerated it, pushing the limits of hand-carvers’ precision and of metallurgy to hold the shape through printing. By 1702 a folio called the Médailles was printed that utilized a class of fonts that is now called transitional roman, and it completely lacked brackets.

Other, subsequent font classes that are, generally, bracketless include modern, slab-serif and of course sans-serif.

Now that we make most of our letterforms from bits, the presence of brackets is mostly a stylistic choice. Visually, brackets reduce the apparent contrast of serif-to-stroke, remove the visual “hot” spots caused by more precise angles, and feel less mechanical and more humanist. Most serifed fonts aimed at elegance adopt the bracket.

Brack"et (&?;), n. [Cf.OF. braguette codpiece, F. brayette, Sp. bragueta, also a projecting mold in architecture; dim. fr.L. bracae breeches; cf. also, OF. bracon beam, prop, support; of unknown origin. Cf. Breeches.]

1. (Arch.)

An architectural member, plain or ornamental, projecting from a wall or pier, to support weight falling outside of the same; also, a decorative feature seeming to discharge such an office.

⇒ This is the more general word. See Brace, Cantalever, Console, Corbel, Strut.

2. (Engin. & Mech.)

A piece or combination of pieces, usually triangular in general shape, projecting from, or fastened to, a wall, or other surface, to support heavy bodies or to strengthen angles.

3. (Naut.)

A shot, crooked timber, resembling a knee, used as a support.

4. (Mil.)

The cheek or side of an ordnance carriage.

5. (Print.)

One of two characters [], used to inclose a reference, explanation, or note, or a part to be excluded from a sentence, to indicate an interpolation, to rectify a mistake, or to supply an omission, and for certain other purposes; -- called also crotchet.


A gas fixture or lamp holder projecting from the face of a wall, column, or the like.

Bracket light, a gas fixture or a lamp attached to a wall, column, etc.


© Webster 1913

Brack"et, v. t. [imp. & p. p. Bracketed; p. pr. & vb. n. Bracketing]

To place within brackets; to connect by brackets; to furnish with brackets.


© Webster 1913

Brack"et, n. (Gunnery)

A figure determined by firing a projectile beyond a target and another short of it, as a basis for ascertaining the proper elevation of the piece; -- only used in the phrase, to establish a bracket. After the bracket is established shots are fired with intermediate elevations until the exact range is obtained. In the United States navy it is called fork.


© Webster 1913

Brack"et, v. t. (Gunnery)

To shoot so as to establish a bracket for (an object).


© Webster 1913

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