parens

Parens, short for parentheses, are punctuation marks used to set off text or to group expressions. The pair consists of an opening parenthesis "(" and a closing parenthesis ")". The plural parens is common in everyday usage; parenthesis is the singular form. They serve to add information, clarify meaning, or indicate a secondary thought within a sentence. For example: The meeting (which started late) finished early.

In prose, parentheses enclose material that is supplementary, optional, or tangential to the main point. The content inside is not required for the sentence to be complete, and it can often be removed without changing the core meaning. Punctuation rules around parentheses vary by style guide, but in general a period that ends a sentence is placed inside the closing parenthesis only if the entire sentence ends there; otherwise the period stands outside.

Beyond writing, parentheses have many uses in mathematics, logic, and computing. They denote grouping to override order of operations, as in (2 + 3) × 4. They surround function arguments, as in f(x), and coordinate pairs, as in (x, y). In programming languages, parentheses appear in expressions, function calls, and control constructs, and they can be nested to multiple levels, requiring careful pairing.

Etymology traces the term to the Greek paréntēsis, from para- “beside” and tithenai “to place.” In typography, parens are part of a broader family that includes square brackets and curly braces, which serve similar but distinct purposes for grouping and hierarchical organization of text and symbols.