1. Dates
2. Addresses
3. Numbers (in the U.S.)
4. After an introductory element
5. To separate a compound sentence that is joined by a conjunction
6. In a list
7. Between adjectives of equal weight
8. To introduce quotations
9. To separate an interjector
10. With dependent clauses
11. With a non-restrictive element
1. Dates
Use a comma after the day and before the year.
EXAMPLE: January 26, 2004
2. Addresses
Use a comma after the city and before the state.
EXAMPLE: San Diego, CA 92101
3. Numbers (in the U.S.)
Starting from the right, use a comma to separate every three numbers.
EXAMPLE: 1,453,654
4. After an introductory element
An introductory element appears before the traditional subject and verb in a sentence. The length of an introductory element can vary from one word to a significantly long phrase. Some people prefer not to include a comma if the introductory element is only one word, like "then". Ask your instructor about his or her preference and make sure you are consistent throughout the document.
EXAMPLE: For the first time in his life, John felt happy.
5. To separate a compound sentence that is joined by a conjunction
Varying your sentence structure is always a good idea to keep the reader interested. However, if you choose to join two sentences, make sure you do it correctly. A comma should be used if a conjunction ("and," "but," or "or") is present. However, if you do not use a conjunction, you will need a semicolon. Please see 1C1 for more information on semicolon use.
EXAMPLE: We went to the theater, and they met us there.
6. In a list
Not all writers agree about the use of commas in a list. You should consult your instructor about his or her preferences. Some people prefer to include a comma after the penultimate item to clarify. Choose one method and be consistent throughout your document. For complex lists, you may need to include semicolons (1C2).
EXAMPLE: The stadium was filled with red, yellow, and green flags.
7. Between adjectives of equal weight
When you use two or more adjectives to describe a noun, put commas between them. Also see the hyphen rules for conveying different meanings with the same words.
EXAMPLE: The dark, shabby coat looked even worse in the sunlight.
8. In quotations
When you use quotations within a sentence, you will need a strong introductory word and a comma. Please notice that the comma is inside the quotation mark. Also remember to include documentation in non-fiction writing.
EXAMPLE:
Theresa commented, "I prefer the brown skirt."
"I prefer the brown skirt," Theresa commented.
9. To separate an interjector
Interjectors are often used rhetorically to add emphasis and delay the meaning of the sentence. Though many words can be used as interjectors, some examples include: however, nevertheless, and alas.
EXAMPLE: Tim never got good grades; he was, however, an excellent artist.
10. With dependent clauses - note: only if the sentence BEGINS with the clause
Similar to an introductory element, a dependent clause uses a comma only when it begins the sentence.
EXAMPLE:
Because the weather was uncooperative, the wedding had to be held inside the lodge.
The wedding had to be held inside the lodge because the weather was uncooperative.
11. With a non-restrictive element
EXAMPLE: "Mark Twain," which was only a pseudonym, quickly became one of the most famous names in American literature.
