When to Use a Comma
The comma is a frequently used type of punctuation that helps separate words and ideas in a sentence. Writers use commas in many different ways.
Commas in a Series
When listing three or more items, insert a comma after all of the items except the last one.
Commas Between Adjectives
When using two or more adjectives to describe someone or something, insert a comma between the adjectives.
Generally, do not insert commas after adjectives that indicate either a number or the size, shape, or age of something or someone.
Commas with Introductory Elements
Insert a comma after introductory words and mild interjections that come at the beginning of a sentence.
Insert a comma after an introductory prepositional phrase if it contains at least one additional prepositional phrase. You don’t need to use a comma if either the sentence starts with just one prepositional phrase (unless you’d naturally pause after saying it aloud) or the prepositional phrase is very short.
Insert a comma after a verbal phrase that comes at the beginning of a sentence.
Insert a comma after an introductory adverb or adverb clause that comes at the beginning of a sentence.
Commas with Interrupters
Insert commas to set off words of direct address, such as names, titles, or terms of respect.
Commas with Nonessential Information
Insert commas to set off nonessential clauses, participles and participial phrases, and appositives and appositive phrases. Nonessential elements add additional information that isn’t necessary for understanding a sentence’s meaning.
Commas in Compound Sentences
Insert a comma before the coordinating conjunction that joins two independent clauses in a compound sentence.
Commas with Quotations
Insert commas in direct quotations to set off words telling who is speaking. Always place a comma inside of a closing quotation mark.
Commas in Dates
Insert a comma between a day of the month and a year. If a date is part of a sentence, then insert a comma after the year as well. If only a month and a year are given with no specific day, then do not include a comma.
Commas in Places
Insert a comma between a city and its state, country, or province. If a place is part of a sentence, then insert a comma after each item in the place’s name.
Commas in Letters
Insert a comma after the salutation of a friendly letter and also after the closing of either a friendly letter or business letter.
Thank you for your gift!
It was great to see you when we were recently in town.
Commas in Names
Insert a comma between a person’s name and any abbreviation or acronym that follows it. Many, though not all, businesses follow a similar practice by inserting a comma between their names and any accompanying abbreviations or acronyms.
Commas in Numbers
In numbers insert a comma after every third digit from the right. (This rule does not apply to zip codes, phone numbers, or house numbers.)