1. Coordinating Conjunctions (FANBOYS):
* For, And, Nor, But, Or, Yet, So
* Use a comma BEFORE the conjunction when it joins two independent clauses (clauses that could stand alone as sentences).
* Example: The dog barked, and the cat hissed.
* Do NOT use a comma when the conjunction joins two words or phrases (not complete sentences).
* Example: The dog barked and ran.
2. Subordinating Conjunctions:
* Because, although, since, while, if, unless, etc.
* Use a comma BEFORE the conjunction when it introduces a dependent clause (a clause that cannot stand alone as a sentence) that comes before the independent clause.
* Example: Because the rain was pouring, we stayed inside.
* Do NOT use a comma when the dependent clause comes AFTER the independent clause.
* Example: We stayed inside because the rain was pouring.
3. Conjunctive Adverbs:
* However, therefore, nevertheless, moreover, etc.
* Use a semicolon (;) BEFORE the conjunctive adverb and a comma AFTER it when it connects two independent clauses.
* Example: The sun was shining; however, the wind was cold.
* Do NOT use a comma if the conjunctive adverb is within a clause.
* Example: The dog was, however, a good boy.
Important Note: There are always exceptions to these rules, and grammar can be nuanced. If you are unsure about comma usage, it's best to consult a grammar guide or a trusted writing resource.