I would use a semicolon before therefore, and no comma after:
[some argument]; therefore [blah blah].
See this Grammar Girl post on how to use semicolons and conjunctive adverbs, such as therefore:
Semicolons with Conjunctive Adverbs and Transitional Phrases
Finally, you use a semicolon when you use a conjunctive adverb or transitional phrase to join two main clauses.
Conjunctive adverbs are words such as “however,” “therefore,” and “indeed,” and they "usually show cause and effect, sequence, contrast, comparison, or other relationships" (1). For example, “I have a big test tomorrow; therefore, I can't go out tonight.” (The comma after the conjunctive adverb is optional.)
A transitional phrase is something like “for example” or “in other words.” A sentence with a transitional phrase could read as follows:
I have a big test tomorrow; as a result, I can't go out tonight.
Coordinating Conjunctions Versus Conjunctive Adverbs
Sometimes people seem frustrated because they have to remember to use commas with coordinating conjunctions and semicolons with conjunctive adverbs most of the time. If you can't keep the difference straight in your head, it can help to remember that commas are smaller than semicolons and go with coordinating conjunctions, which are almost always short two- or three-letter words—small words, small punctuation mark.
Semicolons are bigger and they go with conjunctive adverbs and transitional phrases, which are almost always longer than three letters—bigger words, bigger punctuation.
We typically think of adverbs as modifiers, but conjunctive adverbs are a special breed. Their function is not to modify but to connect. Thus, a conjunctive adverb is an adverb that connects two clauses. Conjunctive adverbs show cause and effect, sequence, contrast, comparison, or another type of relationship.
Examples of conjunctive adverbs include the following:
| accordingly, | furthermore, | moreover, | similarly, |
| also, | hence, | namely, | still, |
| anyway, | however, | nevertheless, | then, |
| further, | incidentally, | next, | thereafter, |
| certainly, | indeed, | nonetheless, | therefore, |
| consequently, | instead, | meanwhile, | thus, |
| finally, | likewise, | otherwise, | undoubtedly, |
Conjunctive adverbs as introductions
Conjunctive adverbs are often used as introductory terms; in this case, these words should be followed by a comma for clarity: Therefore, all of the test animals were re-examined.
This situation also applies to instances in which the conjunctive adverb is the introductory word of a second independent clause: Joe had forgotten his running shoes, and therefore, he could not participate in the race. In this sentence, the first comma is used to separate the first independent clause from the second independent clause, and the second comma is needed after the introductory word therefore. You do not need a third comma between and and therefore.
Note that this example can also be written as follows: Joe had forgotten his running shoes; therefore, he could not participate in the race. The use of the semicolon to separate the two independent clauses is often preferred when the second clause begins with introductory adverbs such as thus, therefore, however, and indeed. Be careful to avoid a comma splice when joining two independent clauses with a conjunctive adverb:
- Incorrect:
- The game was almost lost, however our team scored a goal.
- The game was almost lost, however, our team scored a goal.
- Correct:
- The game was almost lost; however, our team scored a goal.
Other uses
When conjunctive adverbs are not used as introductory words, the placement of commas depends on whether the word is restrictive, or essential to the meaning; that is, is the word required to convey the correct meaning, or would the sentence remain intact if the word were removed? If the word is restrictive, commas should not be used; if the word is nonrestrictive, commas are required.
Here is an example in which therefore is essential to the meaning of the sentence: The students cheated and were therefore disqualified. In this sentence, the disqualification is a direct consequence of the cheating. If therefore were omitted, it would not be clear that the two issues were related.
Here is an example in which therefore serves as more of an aside or a pause: All of the test animals, therefore, were re-examined. In this case, therefore is bounded by commas to separate it from the rest of the sentence and to provide a pause for the reader. Note that in this sentence, no semicolon is needed because it is not a compound sentence. In this example, if therefore were moved and placed within the verb were re-examined, it would be treated as an essential (restrictive) adverb and would not require commas: All of the test animals were therefore re-examined.
We hope that today’s post has increased your understanding of how to use commas with conjunctive adverbs. As always, write to us at [email protected] with any questions. Best wishes from AJE!