brackets

Brackets are punctuation marks used to enclose content within text or to indicate structure in notation. The main types are parentheses (), square brackets [], curly braces {}, and angle brackets <> (also called chevrons). In some contexts the term brackets refers to the set as a whole, while in others it may be used for specific kinds, depending on regional or disciplinary conventions.

In prose and editing, parentheses enclose incidental or optional material. Square brackets indicate editorial insertions, clarifications, or corrections within quoted text. Angle brackets are mostly reserved for technical notation, placeholders, or markup-related content, while curly braces are uncommon in ordinary writing and appear more often in specialized fields such as mathematics or programming.

In mathematics and the sciences, brackets serve different grouping and notation roles. Parentheses group terms and denote function arguments. Square brackets provide a second level of grouping or denote matrices and certain functions. Curly braces denote sets and are used in piecewise definitions. Angle brackets denote inner products, sequence or vector notation, and similar constructs across various disciplines.

In computing and programming, bracket usage reflects language syntax. Parentheses control evaluation order and function calls. Square brackets index into arrays, access elements, or denote optional parameters in some languages. Curly braces define blocks of code or object literals. Angle brackets appear in type parameter lists or in markup languages such as HTML and XML.

Historically, brackets evolved from punctuation marks used to clarify text. Square brackets were introduced for editorial insertions in quoted material, and terminology varies by language and style guide, leading to different conventions for naming and usage across domains.