1. Separating Items in a List:
* Simple List: We bought apples, oranges, and bananas.
* Complex List: He visited London, England; Paris, France; and Rome, Italy.
2. Separating Independent Clauses:
* With Coordinating Conjunctions: We went to the park, and then we had a picnic.
* Without Coordinating Conjunctions: The sun was shining, the birds were singing.
3. Setting Off Introductory Phrases and Clauses:
* Phrases: After the long drive, we were exhausted.
* Clauses: Because she was late, we missed the beginning of the movie.
4. Setting Off Non-Essential Phrases and Clauses:
* Phrases: The dog, a golden retriever, barked loudly.
* Clauses: My brother, who lives in California, is coming to visit.
5. Setting Off Appositives:
* Appositives: My friend, Sarah, is a doctor.
6. Separating Direct Address:
* Example: John, are you ready to go?
7. Separating Dates, Addresses, and Titles:
* Dates: July 4, 1776
* Addresses: 123 Main Street, Anytown, CA 12345
* Titles: "The Lord of the Rings," by J.R.R. Tolkien
8. Setting Off Interjections:
* Example: Wow, that's amazing!
9. In Numbers:
* Thousands and millions: 1,000; 1,000,000
10. For Clarity and Emphasis:
* Example: I saw the cat, not the dog. (This clarifies that the speaker saw the cat, not the dog)
Note: These are just some of the most common uses of commas. There are other specific cases where they are used, and the rules can be complex. It's important to consult a grammar guide or style manual for a comprehensive explanation of comma usage.