Grouping Constructs

(subexpression)Captures the matched subexpression and assigns it a zero-based ordinal number.
(?<name> subexpression)Captures the matched subexpression into a named group.
(?<name1-name2> subexpression)Defines a balancing group definition.
(?: subexpression)Defines a noncapturing group.
(?imnsx-imnsx: subexpression)Applies or disables the specified options within subexpression.
(?= subexpression)Zero-width positive lookahead assertion.
(?! subexpression)Zero-width negative lookahead assertion.
(?<= subexpression)Zero-width positive lookbehind assertion.
(?<! subexpression)Zero-width negative lookbehind assertion.
(?> subexpression)Nonbacktracking (or "greedy") subexpression.