When using the conjunction "not only...but also" (or "not only...but"), place a comma before "but" if the second part of the sentence is an independent clause (that is, if it expresses a complete thought and has a subject and a verb).

When using the conjunction "not only...but also" (or "not only...but"), place a comma before "but" if the second part of the sentence is an independent clause (that is, if it expresses a complete thought and has a subject and a verb).

Not only does Peter speak Spanish, but he speaks Japanese.

Not only does Peter speak Spanish but he speaks Japanese.

If "but also" is followed by a dependent clause or a phrase, the comma is optional.

Not only did my sister eat a pizza but also a whole chicken.

1. Quick Grammar Review of the Structure 'Not only...but also'

We use the structure "not only...but also" when we want to emphasize two similar or closely related ideas.

Isabella is not only intelligent but also cute.

When using this correlative conjunction, both parts of the sentence should be balanced; that is, they should have the same grammatical structure.

Spanish food is not only quite healthy but also pretty cheap.

We can add even more emphasis by using "not only" at the start of the clause. When we do this, we invert the subject and the auxiliary verb.

Not only does Richard play tennis, but also he plays badminton.

2. When to Put a Comma Before 'but also'

We should put a comma before "but" to separate two independent clauses.

Not only did Robert fail the exam, but also he dropped out of college.

Not only did Robert fail the exam but also he dropped out of college.

An independent clause is a group of words that can form a complete sentence standing alone ("did Robert fail the exam" and "he also dropped out of college" in the sentence above).

Follow the same comma rule with other correlative conjunctions.

More examples:

• Not only will you learn punctuation, but also you'll put it into practice.
• Not only can Claire speak English, but also she can speak Spanish.

3. The Optional Comma

If the second clause is not an independent clause, you can optionally add a comma before "but also".

My brother likes not only playing video games, but also watching horror movies.

Some writers leave out this comma when the second part of the sentence is short and clear.

Albert visited not only Vietnam but also Laos.

It will snow not only today but also tomorrow.

But you can put a comma to add more emphasis.

Rebecca is not only intolerant, but also bossy.

He reads not only philosophy books, but also metaphysics essays.

More examples:

• Jennifer has taught English not only in the US, but also in other countries.
• James is not only rude but also lazy.
• Learning Japanese helps me not only find a new job, but also connect with Japanese traders.
• Learning Chinese in a classroom is not only time-consuming but also expensive.

4. Placing a comma before 'Not only'

There are particular situations where you may need a comma before "not only". For example, add a comma after an introductory phrase or word.

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More examples:

• On a rainy day, not only do I feel irritable, but also I feel moody.
• Actually, not only does William play the guitar, but also he writes his own songs.
• When eating healthy food, not only do I feel better, but also I lower my sugar levels.