Conjunctive adverbs look like coordinating conjunctions (and, but, or, so, for, yet, nor); however, they are not as strong as coordinating conjunctions and they are punctuated differently.

A conjunctive adverb is also used in a single main clause. In this case, a comma (,) is used to separate the conjunctive adverb from the sentence.
Ex : I woke up very late this morning. Nevertheless, I wasn’t late to school.
She didn’t take a bus to work today. Instead, she drove her car.