Brackets are punctuation marks used in pairs to set apart or interject text within other text. In computer science, the term is sometimes said to strictly apply to the square or box type.

There are four main types of brackets:

• round brackets, open brackets, or parentheses:  ( )
• square brackets, closed brackets, or box brackets:  1
• curly brackets or braces:  { }
• angle brackets, diamond brackets, cone brackets, or chevrons:  < > or

History

The angle bracket was the earliest type to appear in English. Desiderius Erasmus coined the term lunula to refer to the rounded parentheses (), recalling the round shape of the moon.

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 (round bracket).

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. In more formal usage “parenthesis” may refer to the entire bracketed text, not just to the punctuation marks used (so all the text in this set of round brackets may be said to be a parenthesis).

Parentheses ( )

Parentheses (singular, parenthesis)—sometimes called round brackets, curved brackets, oval brackets, or just brackets, or, colloquially, parens — contain material that could be omitted without destroying or altering the meaning of a sentence.

Parentheses may be used in formal writing to add supplementary information, such as “Sen. Edward Kennedy (D., Massachusetts) spoke at length.” They can also indicate shorthand for “either singular or plural” for nouns—e.g., “the claim(s)”.

Parenthetical phrases have been used extensively in informal writing and stream of consciousness literature. Of particular note is the southern American author William Faulkner (see Absalom, Absalom! and the Quentin section of The Sound and the Fury) as well as poet E. E. Cummings. In most writing, overuse of parentheses is usually a sign of a badly structured text. A milder effect may be obtained by using a pair of commas as the delimiter. If the sentence contains commas for other purposes visual confusion may result.