Comma needed when connecting two independent clauses. Independent clauses can stand alone with subject and verb. Second subject can be omitted to make second clause independent
Conjunctions connect words, phrases, clauses, or sentences together. Seven coordinating conjunctions (FANBOYS) are commonly used. Conjunctions can be single words or phrases like "even though"
Comma before "and" is optional in lists of two items. In lists of three or more, use Oxford comma (serial comma). MLA Style Book uses serial comma, AP Style Book doesn't. Serial comma helps avoid confusion in lists
Use comma before "but" in compound sentences with two independent clauses. Independent clauses can stand alone as complete sentences. Dependent clauses lack subjects and verbs and don't need commas
Comma needed before 'but' when second clause has subject and verb. Independent clauses can stand alone and form complete sentences. Same rules apply to coordinating conjunctions like 'and', 'or', 'so'
No comma needed when 'because' is used in clear sentences. 'Because' joins independent and dependent clauses. Same subject clauses should repeat after 'because'