Have you ever wondered how to use a comma with however (or if you even should)? Here's the scoop on using commas and semicolons with however, therefore, and other conjunctive adverbs and transition words.
Two weeks ago, we talked about comma splices—errors that happen when you join two main clauses with just a comma--but you can make the same kind of mistake if you aren’t careful when joining two main clauses with conjunctive adverbs such as however, therefore, furthermore, and nevertheless.
Two Main Clauses
Remember, a main clause, also known as an independent clause, is just something that could be a complete sentence if it were all by itself. If you’re joining two main clauses with a conjunctive adverb, you need a semicolon before that adverb, and a comma after. That adverb needs to be snuggled between a semicolon and a comma.
Think about this example. Imagine I’m worried about a library book that is due tomorrow:
I’m not finished reading it; moreover, I left it at Steve’s house.
I’m not finished reading it is a main clause, and I left it at Steve’s house is a main clause, so I need a semicolon before moreover and a comma after it.
Or, in the same way you can fix a comma splice with a period, I could also separate the two main clauses with a period:
I’m not finished reading it. Moreover, I left it at Steve’s house.
Adverbs in the Middle
This is where it gets tricky because sometimes conjunctive adverbs come in the middle of your sentence and aren’t followed by a main clause, and then you can just sandwich them between two commas. Here are some examples of sentences like that:
I’ll wager, moreover, that the library won’t cut me any slack on the fine.
Fines are, however, an important tool the library uses to get people to return books on time.
In both those sentences, the part after the adverb isn’t a main clause, so I just used a comma before and after the words moreover and however.