Each of these requires a comma when combining two independent clauses (sentences).
- “for” is also a preposition
- “and,” “nor,” “or” combine nouns, verbs, adjectives, adverb , prepositional phrases, and more
- “but” is also a preposition, an adverb, and occasionally a pronoun
- “so” is also an adverb, an adjective, and even a pronoun
- The king, his horses, and his men tried to pick up all the pieces, for Humpty Dumpty had fallen from the wall.
- (The first “and” between “horses” and “his men” is part of a list, not combining independent clauses.)
- (Two independent clauses/sentences combined with “for”)
- The men picked up the pieces for the king.
- (“For” = preposition, not conjunction)
- The men put the pieces into baskets, and the horses carried them to the palace.
- (Two independent clauses/sentences combined with “and”)
- The men and the horses worked all day.
- (“And” = conjunction creating a compound subject rather than combining independent clauses)
- The men couldn’t put the pieces together, nor could the king.
- (Two independent clauses/sentences combined with “nor”)
- (The second clause has the subject and verb reversed.)
- Neither the king nor the queen slept that night for grieving over the loss of the egg.
- (“Nor” = correlative conjunction creating a compound subject rather than combining independent clauses)