Parenthesis

A parenthesis is a punctuation mark in the form of a curved line used to enclose material that is supplementary or aside from the main text. The singular term is “parenthesis,” while the plural is “parentheses.” They are commonly called round brackets in many varieties of English. The function is to insert information that clarifies or comments but is not essential to the main point. They can enclose explanations, examples, abbreviations, or numerical references, and they may indicate optional words or phrases.

In writing, parentheses serve to set off aside material, to indicate nonessential or explanatory content, or to enclose references such as citations or numbers from lists. They can also be used to enclose acronyms on first mention or to mark optional text. Typographic practices vary by style guide; some guides recommend avoiding overuse to prevent interrupting flow.

In mathematics and computing, parentheses denote grouping of terms, function arguments, and order of operations. They define intervals in mathematics, such as (0, 1) for an open interval. In programming languages, parentheses are used for function or method calls, to control precedence, and to create tuples or parameter lists in some languages.

Typography and conventions: punctuation rules around closing parentheses depend on the surrounding sentence. In American practice, if the parenthetical material forms a complete sentence or the entire sentence is within parentheses, the period typically goes inside the closing parenthesis; otherwise it goes outside. When nesting, inner parentheses are often distinguished by using a different bracket type (for example, ( [ ] )).

History and terminology: the word derives from Greek para beside and histithesis placing. The marks appeared in English during the early modern period and have become standard in many languages. Related marks include square brackets, curly braces, and angle brackets, which are used for nested or editorial material.