Therefore and Too are conjunctive adverbs, and they cause a lot of problems with commas. Before we look at using commas with therefore and too, we need to understand conjunctive adverbs and what they do.
What Conjunctive Adverbs Do
A conjunctive adverb shows how the idea in one sentence or independent clause is related, or connected, to the idea in the previous sentence or independent clause. Conjunctive adverbs include such words as additionally, finally, however, indeed, in fact, rather, similarly, therefore, thus, and too.
Let’s look at an example to see how conjunctive adverbs affect meaning.
She left early. Therefore, he was lonely.
She left early. He was lonely.
In the first example, we know that her early departure caused his loneliness. Therefore indicates a cause and effect relationship between the two sentences. The conjunctive adverb connects the idea in sentence two to the idea in sentence one. It indicates how he was lonely relates to She left early.
Without the conjunctive adverb (second example), the two sentences present two unrelated ideas. What does his loneliness have to do with her early departure. In the second example, nothing.
Commas with Conjunctive Adverbs
When the conjunctive adverb is at the beginning of the first example, it needs to be followed by a comma to separate it from the rest of the sentence (Zen Comma Rule N). Let’s look at another example sentence.
The town flooded; as such, the field is unusable.
In this example, the conjunctive adverb as such is the first word of the second independent clause. (Notice the semicolon that joins the two clauses.) It is also followed by a comma to separate it from the information that follows it.
These examples demonstrate the most common placement for the conjunctive adverbs: at the beginning of the sentence. However, like all adverbs, conjunctive adverbs can be moved to various locations in an independent clause, as in the next example.
I, too, am ready for dinner.
This example, with too…