A period is used to end a sentence. A period is used inside quotation marks at the end of a sentence. Exclamation Point 1. Questions Marks 1. Commas are used between two independent clauses separated by a conjunction, and the comma appears before the conjunction.
Conjunctions are such words as and, but, for, nor, or, so, and yet.
Other adverbs commonly used to start sentences include after, if, as, because, and although. A nonrestrictive clause, which is a clause that could be dropped from a sentence without changing the meaning of the sentence, is often set off with commas. A clause that begins with a form of a verb is set off with a comma from the rest of the sentence. Having explained this rule, I will now move on to the next rule. Parenthetical words, phrases, and clauses should be set off with commas.