The Editor’s Manual
Free learning resource on English grammar, punctuation, usage, and style.
Parentheses (round brackets) are the most commonly used brackets in English, followed by square brackets. The other two types of brackets are braces and angle brackets. Each type serves a different purpose.
Brackets enclose editorial comments and corrections, and any text added to a quote by someone other than the original writer. “Sic” in brackets indicates an exact reproduction. Brackets also set off parenthetical material that appears in text already within parentheses.
Use parentheses (or round brackets) to set off supplementary information from surrounding text. Such information should not be essential to the grammar of the sentence. Periods go within parentheses if they belong to the parenthetical matter but outside otherwise.
Use commas to make lists, set off phrases, separate clauses, and indicate that a detail is nonessential in a sentence.
Use a comma between the items in a list, to separate two independent clauses, and after a subordinate clause. Enclose nonessential phrases and clauses in commas.
Use em dashes to set off parenthetical statements, amplify a thought, begin a sentence with a list or a single noun and then provide an explanatory statement, or to mark asides, interruptions, and sudden turns in thought.