How to Use a Comma: 9 Comma Usage Rules to Follow

A comma is a punctuation mark that denotes a break between clauses within a sentence. Commas suggest a soft pause between clauses in a sentence which gives the reader a moment to breathe before finishing the rest of the sentence. In writing, commas also separate sentence clauses, denote extra information about a subject, and divide items in a series of words. Many writers use commas in incorrect places because they mistake the rhythmic rules of speaking for the proper rules or writing. Using commas correctly in your writing can clarify the meaning of a sentence and give your words a natural rhythm.

Here are some basic rules for comma usage that you can follow to ensure that your writing is grammatically correct.

1. 1. Separate two independent clauses joined by a conjunction with a comma. Commas are used to join one independent clause (containing a subject, object, and verb) to another independent clause within a sentence. If your sentence has two independent clauses, you can join them by placing a comma after the first part of the sentence and following it with a coordinating conjunction such as "and" or "but.” For example, it is correct to write: "I love my dog, but I hate when he barks."
2. 2. Use a comma after an introductory phrase. A comma follows a participial which is an introductory clause or phrase at the beginning of a sentence that depends on the next clause of your sentence, which is independent. For example, it is correct to write: “Earlier that day, John went shopping."
3. 3. Use a comma after a conjunctive adverb. A conjunctive adverb is a transitional word that can either join two related sentence clauses or introduce a sentence. Some conjunctive adverbs include: however, nevertheless, furthermore, also, hence, anyway, and moreover. Use a comma after a conjunctive adverb, whether it comes at the beginning of a sentence or in the middle.
4. 4. Divide separate items in a list using commas. Use commas to divide items in a list of nouns or coordinate adjectives. To separate three nouns you could write: "Hannah bought eggs, milk, and cheese." To separate three adjectives you could write: “James is healthy, happy, and strong.” If there is a list of items with a list of clauses, semicolons are used in place of the commas dividing the list of clauses. For example, it would be correct to write: "Hannah rode to the store; she bought eggs, milk, and cheese."
5. 5. Oxford or serial commas are optional. When you are dividing a list of items, the Oxford comma, also known as the serial comma, is the final comma in a list of subject words, following the second last item which usually precedes “and.” For example, without an oxford comma a list would read: "eggs, milk and cheese." With an oxford comma, the list would read "eggs, milk, and cheese."
6. 6. Separate nonrestrictive clauses with a comma. A nonrestrictive clause provides nonessential information about the main clause of a sentence. Nonrestrictive clauses, which typically reveal additional information about a subject, are placed after the subject of the sentence after a comma. The nonrestrictive clause is closed with a comma which makes it similar to a parenthetical. For example, it would be correct to write: "Hannah, who had no food left in the house, went to the store to buy eggs."
7. 7. Separate an appositive from a subject with a comma. An appositive is a noun or noun phrase that adds information to the primary noun. You will need to use commas to separate this type of phrase from the rest of your sentence to prevent it from running on. For example, it would be correct to write, "Alex, a renowned painter, presented his new work at the gallery."
8. 8. Use commas to set off a direct quotation. A comma should be used to introduce and end a direct quotation when it's not at the end of the sentence. In this case, the last comma in the quotation takes the place of other punctuation (like a question mark or exclamation point) and should be located inside the end quotation marks. For example, it is correct to write: "The boy looked up and said, 'I'll play,' before joining the game." You should also use a comma to introduce a quote that is attributed to a particular subject. For example, it would be correct to write: “Jamie said, ‘I don’t have time for that today.’”
9. 9. Use commas to separate a specific date from the rest of a sentence. Place a comma after the year if you are referencing a specific date in day/month/ year format within a sentence. For example, it is correct to write: “March 17, 1988, was the day that my parents met.”

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