Use a comma before "and" when:
* It connects two independent clauses:
* Example: The dog barked, and the cat ran away. ("The dog barked" and "the cat ran away" can both stand alone as complete sentences.)
* It introduces a series of three or more items:
* Example: We went to the store for milk, eggs, and bread.
* It helps to avoid ambiguity:
* Example: I went to the park with my dog, and my sister. (Without the comma, it's unclear if you went to the park with both your dog and sister.)
Do not use a comma before "and" when:
* It connects two words or phrases that are not independent clauses:
* Example: I went to the store and bought milk. ("I went to the store" is not a complete sentence.)
* The two items being joined are very short and closely related:
* Example: I ate pizza and drank soda. (There's no need for a comma because the two items are very short and clearly connected.)
In general:
If you're unsure whether to use a comma, read the sentence aloud. If you naturally pause before "and," then a comma is probably necessary.
Examples:
* Comma needed: The sun was shining, and the birds were singing.
* Comma not needed: I went to the beach and swam in the ocean.
Remember, the best way to be sure is to consult a style guide or grammar resource.