comma

A punctuation mark that separates sentence elements and clarifies how they relate.

Place commas by sentence structure and meaning, not by pauses. The belief that a comma marks wherever a speaker would pause or take a breath is a myth. In The documents on the highest shelf belong to Mara, a speaker might pause after shelf, but a comma there would wrongly separate the subject from its verb. In Yes, I agree, the comma after Yes is required even though most speakers don’t pause there.

Use commas between items in a series: We ordered folders, labels, and envelopes. The comma before the final and is the Oxford comma, also called the serial comma. Use it or omit it consistently, and add it wherever omitting it would cause a misreading.

Put a comma before a coordinating conjunction that joins two independent clauses: The doors were locked, but a window was open. When two verbs share one subject, omit the comma: She checked the address and rang the bell.

Put a comma after an introductory subordinate clause: When the delivery arrives, call me. Put one after an introductory participial phrase: Carrying two heavy boxes, Nina entered the office. Omit it after a short introductory phrase when the sentence reads clearly without it: By noon the office was empty.

Use paired commas to set off a parenthetical element within a sentence: The application, according to the clerk, was incomplete. When the element ends the sentence, one comma sets it off: The application was incomplete, according to the clerk.

Set off nonessential information with commas. Nonessential information adds detail about something already identified, and the sentence keeps its meaning without it. Information that identifies which one is meant is essential and takes no commas. In The tenants who reported leaks received a notice, the clause tells which tenants received a notice, so it takes no commas. In The tenants, who reported leaks, received a notice, every tenant received a notice, and the clause adds that they reported leaks.

Set off a name or title used in direct address: Please check the total, Morgan. Put a comma after an opening yes or no: Yes, the total is correct.

Separate coordinate adjectives with a comma: It was a lengthy, difficult negotiation. Each adjective describes the noun independently. Cumulative adjectives take no comma: She carried a small black bag. Here small modifies black bag.

Separate quoted speech from its speech tag with a comma: “The figures are correct,” she said. A question mark or exclamation point takes the place of that comma: “Are the figures correct?” she asked. A comma next to a closing quotation mark goes inside it.

Commas have set uses in dates, place-names, and numbers: On August 14, 2025, we opened the office. The shipment came from Tucson, Arizona. The warehouse holds 12,500 cartons. Years take no comma: 2025.

Join independent clauses with a comma only when a coordinating conjunction follows it. The alarm sounded, everyone left is a comma splice. Write The alarm sounded, and everyone left, or separate the clauses with a period or semicolon.

Examples

Use The crew sanded the deck, painted the rails, and coiled the ropes. (Commas separate three actions in a series.)

Use The bakery had sold out, so we ordered a cake for Saturday. (The conjunction joins two independent clauses.)

Use Once the votes were counted, the chair announced the result. (The introductory subordinate clause takes a comma.)

Use The rent, however, has gone up again. (Paired commas set off the parenthetical word.)

Use Theo, please lock the side door. (The name is used in direct address.)

Avoid The tools stored in the garage behind the house, need cleaning. (Delete the comma between the subject and its verb.)

Avoid The train was late, we missed the opening speech. (A comma cannot join two independent clauses by itself; this error is called a comma splice. Use a period or semicolon, or add a coordinating conjunction such as so after the comma.)