1. Joining Independent Clauses
* Use a comma + conjunction (and, but, or, nor, for, so, yet): This separates two complete sentences that can stand alone.
* Example: "The sun was shining, but the wind was cold."
2. Introductory Phrases and Clauses
* Use a comma after a short introductory phrase: "After dinner, we went for a walk."
* Use a comma after a longer introductory phrase or clause: "Because of the rain, we decided to stay inside."
* Use a comma after introductory words like "however," "therefore," "moreover," "consequently," etc.: "However, she did not agree with his plan."
3. Lists and Series
* Use commas to separate items in a list: "We need apples, oranges, bananas, and grapes."
* Use a comma before the conjunction "and" in a list of three or more items: "He bought a car, a house, and a boat."
4. Non-essential Phrases and Clauses
* Use commas to set off words, phrases, or clauses that aren't essential to the meaning of the sentence:
* "My friend, who is a doctor, gave me some advice." (The clause "who is a doctor" is extra information.)
* "The house, built in the 1920s, is now a museum." (The phrase "built in the 1920s" is extra information.)
5. Direct Address
* Use a comma after a direct address: "John, can you please pass the salt?"
6. Dates and Addresses
* Use commas to separate elements in dates: "December 12, 2023"
* Use commas to separate elements in addresses: "123 Main Street, Anytown, CA 12345"
7. Numbers
* Use commas to separate thousands, millions, etc.: "1,000,000"
8. Misplaced Commas
* Avoid placing commas between the subject and verb: "The dog, barked loudly." (Incorrect)
* Avoid placing commas between the verb and object: "She walked, the dog." (Incorrect)
9. Other Considerations
* Oxford comma (serial comma): Use a comma before the final "and" in a list to avoid ambiguity.
* "I like cats, dogs, and hamsters." (Oxford comma)
* "I like cats, dogs and hamsters." (No Oxford comma - potentially confusing if "dogs and hamsters" is a single unit)
Important Note: These rules are general guidelines. Context and the intended meaning of the sentence can sometimes influence the use of commas.
For More Help:
* Online Grammar Checkers: These can help identify common comma errors.
* Style Guides: Consult specific style guides like the Chicago Manual of Style or the MLA Handbook for more in-depth rules.