comma

The comma is a punctuation mark used to indicate a short pause within a sentence and to separate items or clauses. It helps clarify meaning, control rhythm, and prevent misreading by marking boundaries where a full stop is not warranted.

In English, commas are commonly used to separate items in a list (apples, oranges, and bananas), to set off introductory phrases (For example,), to enclose nonessential information (The book, a bestseller, was published in 2020), and to join independent clauses with a coordinating conjunction when desired emphasis is light (It was late, but we finished). They also appear in dates, addresses, and large numbers (July 4, 1776; 1,000).

The serial or Oxford comma—the comma before the conjunction in a list—is optional and varies by style guide. Its presence can affect clarity (We invited the performers, not the crew).

Regional differences exist: in many languages the comma also functions as a decimal separator, and in others as a thousands separator, reflecting different numeric conventions. In computing, comma usage is determined by language syntax and data formats.

Historically, punctuation marks indicating pauses have ancient roots, but the modern comma emerged with early printers and was gradually standardized in the modern era.