When should you use a comma and when should not? It could be a life or death matter. After all, “Let’s eat Grandma” is considerably different than “Let’s eat, Grandma.” Sometimes these mechanics and grammar rules do serve a purpose.
Here’s the 22 comma rules from The Pennington Manual of Style to answer all of your comma questions. Want the whole manual including 22 comma rules, 22 capitalization rules, 22 other punctuation rules, 22 quotation marks, italics and underlines, and 22 Modern Language Association (MLA) citation formats? . The author (authority) of these mechanics rules is Mark Pennington, publisher of Teaching Essay Strategies designed to teach students the Common Core W.1 argumentative and W.2 informational explanatory essays with downloadable e-comments, and the newly released Grades 4-8 Grammar, Usage, Mechanics, Spelling, and Vocabulary (Teaching the Language Strand), designed to help students catch up and keep up with grade-level Standards in grammar, usage, mechanics, spelling, and vocabulary.
The Pennington Manual of Style: 22 Comma Rules
1 Speaker Tag In dialogue sentences, place commas after a beginning speaker tag to the left of the quotation marks. Question marks and exclamation points can also separate speaker tags from dialogue. Example: He said, “I shouldn’t listen to what you say.”
2 Speaker Tag In dialogue sentences, place commas before and after a middle speaker tag to the left of both quotation marks. Question marks and exclamation points can also separate speaker tags from dialogue. Example: “But if you don’t,” he shouted “you will never win.”
3 Speaker Tag In dialogue sentences, place commas before an ending speaker tag to the left of the quotation marks. Question marks and exclamation points can also separate speaker tags from dialogue. Example: “Okay. I will give you another chance,” he responded.
4 Appositive Use commas to set apart appositives. An appositive is a noun or pronoun placed next to another noun or pronoun to identify, define, or describe it. The appositive can be a word, phrase, or clause. Example: That man, the one with the hat, left town quickly.
5 Commas in Series Use commas after each item in lists (except the last). Use commas after each item in lists, except the last one. Example: John, Jane, and Jose left early.
6 Introductory Word Use commas only after introductory words which receive special emphasis. Examples: Conversely, you could listen. Then I went home.
7 Introductory Phrase Use commas after introductory phrases when followed by a modifying noun or pronoun . Example: Bold and beautiful, the statue was popular. Don’t use commas if the phrase modifies the following noun or pronoun or if another part of speech follows the phrase. Examples: A bold and beautiful statue was popular. Bold and beautiful was the popular statue.
* Exception: Avoid using commas after short (four words or less) introductory prepositional phrases. Examples: Under the tree he hid. Under the shady oak tree, he hid.
8 Introductory Dependent Clauses A dependent clause includes a noun or pronoun and connected verb, but does not express a complete thought. Place a comma following introductory dependent clauses. Examples: Even though I listened, I didn’t understand.
9 Ending Dependent Clause A dependent clause includes a noun or pronoun and connected verb, but does not express a complete thought. Don’t place a comma before an ending dependent clause. Example: I never got her letter although she did write.
10 Geography Place commas between related geographical place names and after the last place name, unless it appears the end of a sentence. When the place name is a possessive, this rule does not apply. Examples: She lived in Rome, Italy, for a year. Rome, Italy’s traffic is congested.
11 Dates Use commas to separate number dates and years. Don’t place a comma following the year. Example: It all happened on May 3, 1999. On May 4, 1999 we went back home.
12 Beginning Direct Address Use commas to separate nouns of direct address. The noun can be a word, phrase, or clause. If at the beginning of the sentence, one comma follows. Examples: Kristen, leave some for your sister. Officer Daniels, I need your help. Whoever you are, stop talking.
13 Middle Direct Address Use commas to separate nouns of direct address. The noun can be a word, phrase, or clause. If in the middle of the sentence, one comma goes before and one follows. Examples: If you insist, Dad, I will. If you insist, Your Honor, I will.
14 Ending Direct Address Use commas to separate nouns of direct address. The noun can be a word, phrase, or clause. If at the end of the sentence, one comma goes before the noun. Examples: Just leave a little bit, honey. Just leave a little bit, best girlfriend.
15 Compound Sentence Use commas before coordinating conjunctions to join two independent clauses if one or more of the sentences is long. Example: I liked her, and she definitely said that she liked me.
16 Commas to Enclose Parenthetical Expressions Use commas before and after words that interrupt the flow of the sentence. If the interruption is minimal, you may leave out the commas. Example: The best way to see the game, if you can afford it, is in person.
17 Commas to Set Off Non-restrictive Clauses A nonrestrictive clause can be removed from a sentence without changing the meaning of the sentence. The relative pronouns who, whom, whose, and which, but not that, begin nonrestrictive relative clauses. Use commas to set off nonrestrictive relative clauses from the noun or pronoun before the clause. Example: The girl, who sits in the corner, is sleepy.
18 Commas and Restrictive Clauses A restrictive clause can’t be removed from a sentence without changing the meaning of the sentence. A restrictive clause limits the meaning of the independent clause to which it is attached. Don’t use commas before and after restrictive clauses. Example: The student who wins the most votes will be elected Student Council President.
19 Comma and Abbreviations These abbreviations: Sr. (senior), Jr. (junior), and etc. (et cetera) are always preceded by a comma. Don’t place commas after these abbreviations. Examples: Howard, Sr. had Howard, Jr., take out the trash, water the lawn, pull weeds, etc.
20 Comma and Duplicate Words Place commas between repeated words when needed to improve clarity. Examples: Tommy and Pam moved in, in May.
21 Comma to Replace Missing Words Use commas to replace omitted words, especially the word that. Examples: I am a vegetarian; my wife, a meat-eater. Win some, lose some. What I mean is, she hasn’t changed her diet and followed mine.
22 Comma in Parenthetical Citations Place a comma after each author’s name, except the last in a multiple author citation. Don’t use a comma between the author(s) and the page number(s). Example: (Peabody, Jones, and Smith 14) Don’t place a comma between different authors or resource titles citing information; use a semicolon.
Examples: (Peabody 16; Jimenez 55) (The Nature of Change; Wrong Policy)