Compound Sentence with Transitional Word

When a transitional word joins two independent clauses, the usual pattern is a semicolon before the transitional word and a comma after it. (The common transitional words of this type are accordingly, consequently, furthermore, however, moreover, nevertheless, therefore.) The pattern looks like this:

Compound sentence with transitional word

Note: If the transitional word is separating independent clauses — each of which has its own subject and verb, and each of which could stand alone as a sentence — you may correctly use either a semicolon or a period to separate the independent clauses. Do not use the semicolon if the transitional word is not separating independent clauses.

Independent clause followed by a transitional word: semicolon or period before the transitional word

Incorrect—with comma before:

We have not received your reservation, therefore, our assumption is that you will not be attending the meeting.

Correct—with a semicolon (or period) before:

We have not received your reservation; therefore, our assumption is that you will not be attending the meeting.

or

We have not received your reservation. Therefore, our assumption is that you will not be attending the meeting.