When to use a comma with “Not only…but also”?

Grammar / By

Though they are long and not as easy to write as one-clause sentences, “Not only…but also” sentences are not as complicated as they may seem. They do have a few special considerations to them, though, especially when it comes to punctuation with a comma.

In general, you should use a comma after “not only” if you are connecting two independent clauses. If you are connecting two nouns or dependent clauses, you should omit the comma. The key is to maintain parallelism in the phrase.

Here’s your quick guide to using commas in “Not only…but also” sentences, as well as a few general tips for writing them more effectively.

How to Properly Use Commas with “Not only…but also”

Most “Not only…but also” sentences won’t require a comma. It’s a correlative conjunction, which means that it is used to connect two ideas into a single sentence. Because of this, you often don’t have full, independent ideas working together. So, adding a comma would be confusing.

My car is not only fast, but also efficient. The pause here makes little sense as “but also efficient” is not an independent phrase needing separation.
My car is not only fast but also efficient. These are two short ideas combined into a complete thought, so no comma is needed.
On rare occasions, though, you do have two completely stand-alone ideas sharing a sentence. This is often done for dramatic effect, and so will need a comma to indicate the pause between ideas.

Not only is this Matthew’s behavior upsetting but it is also causing serious disruptions in class. The lack of a comma makes this sentence clunky and difficult to read.
Not only is this Matthew’s behavior upsetting, but it is also causing serious disruptions in class. Now it is clear where one clause ends and the next begins, making the sentence more digestible.

The idea with a comma in “Not only…but also” sentences is to make it easier to understand where the emphasis lies and what the subject is. You can include a comma in dependent clause phrases, but only in informal writing where you’re trying to show special emphasis. It’s best to avoid doing so in formal or academic writing.

Other Common Mistakes with “Not only…but also”

An important part of writing with “Not only…but also” is parallelism, or making sure that both sides of the sentence match in terms of tone and structure. It’s best to avoid mixing independent and dependent clauses in these sentences, as that can be confusing to read.

The dogs were not only being checked by the vet, but also fed. This sentence ends more abruptly than it should, and feels unbalanced.
The dogs were being not only checked by the vet but also fed. Moving the verb “being” outside of the “not only…but also” structure balances the clauses by making them both dependent.
Note the removal of the comma in the corrected phrase. On that same idea, when it does come to verbs inside the “Not only…but also” phrase, there should be one in each clause to maintain that balance. You can solve balance issues in multiple ways. Here’s an example:

These changes present not only a better outlook for our community, but they can also improve the college board drastically. This sentence reads oddly as it’s trying to combine a dependent clause and an independent clause.
These changes not only present a better outlook for our community but also improve the college board drastically. Moving the verbs into the phrase and making both phrases dependent fixes the disagreement.
Not only do these changes present a better outlook for our community, but they also improve the college board drastically. Making both clauses independent also serves to solve the issue.

When in doubt, try splitting the “Not only…but also” phrase into its respective parts. Either they should both work as independent sentences, or neither of them should. If one is independent and the other is not, then you need to correct one of the phrases to maintain parallelism.

Conclusion

Not only are these phrases relatively simple to use, but they can also improve the quality of your writing. The key is to use them correctly so that your reader grasps why it’s important to know both parts of the phrase.

As long as you keep the idea of appropriate pauses between clauses and sentence balance in your mind while you’re writing, you should be able to place commas easily and know when you don’t need them at all.

Conor
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