- Use commas to separate three or more words, phrases, or clauses in a series.
- Use a comma after two or more introductory prepositional phrases, after a long introductory phrase, or when a comma is needed to make the meaning clear.
- Use a comma after introductory participles and introductory participial phrases.
- Use commas to set off words that interrupt the flow of thought in a sentence.
- Use commas to set off an appositive.
- Use commas to show a pause after an introductory word or to set off names in direct address.
- Use a comma before and, or, or but when they join independent clauses.
- Clause: a group of words that has a subject and a predicate Independent clause : can stand alone as a sentence Subordinate or dependent clause: cannot stand alone as a sentence Use a comma after an adverb clause that introduces a sentence. Adverb clauses begin with subordinating conjunctions such as after, although, as, because, before, considering (that), if, in order that, since, so that, though, unless, until, when, whenever, where, wherever, whether, or while. Usually commas are not used with adverb clauses that come at the end of a sentence.
- Use commas before and after the year when it is used with both the month and the day. Do not use a comma if only the month and year are given.
- Use commas before and after the name of a state or a country when it is used with the name of a city. Do not use a comma after the state when it is used with a zip or postal code.
- Use a comma to set off an abbreviated title or scholastic degree following a person’s name.
- Use a comma before too when it means “also.”
- Use a comma or a pair of commas to set off direct quotations.
- Use a comma after the salutation of a friendly letter and after the closing of a business letter.
- Use a comma to prevent misreading.