The Editor's Manual
Free learning resource on English grammar, punctuation, usage, and style.
Use a colon only after a grammatically complete sentence to introduce a list. Don’t use a colon between a verb and its object. Don’t use a colon after a title, heading, or caption for a list.
Use a colon to introduce a list or a quotation, or to explain and amplify a statement. It directs the reader’s attention to the information that follows. It can also serve as a sign or separator.
The serial comma is used before the conjunction (“and,” “or”) that marks the final item in a series. Using it is optional, but it can sometimes affect the meaning of a sentence.
Use the “either-or” and “neither-nor” to affirm or negate the one or the other of two alternatives. Make sure that the elements joined using “or” and “nor” are grammatically balanced and parallel in structure.
Use commas to make lists, set off phrases, separate clauses, and indicate that a detail is nonessential in a sentence.
A list may be horizontal or vertical. List elements must be consistently punctuated and capitalized. Use a numbered list when the sequence or number of items is important; otherwise, use bullets.
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.
Use a semicolon in place of a period to join two closely related sentences. Also use it to separate list elements that themselves contain punctuation.