Generally speaking, commas are used to indicate a pause or break in a sentence. They can be used to separate clauses, to indicate a pause between items in a list, to set off nonessential phrases and clauses, and to separate independent clauses when they are joined by coordinating conjunctions (for, and, nor, but, or, yet, so). Commas should also be used when addressing someone directly, when introducing a quote, and after introductory words and phrases.