The structure not only… but also is a particularly useful grammatical construction for Cambridge English exams. It allows you to connect two related ideas while placing emphasis on both of them.
Although it can be used in spoken English, it is more common in written English, making it especially useful in the Writing paper of the B2 First, C1 Advanced and C2 Proficiency exams.
It is also a structure worth learning because it demonstrates your ability to use more sophisticated ways of linking ideas. However, there are several grammatical rules to remember, and students often make small mistakes when trying to use it.
Let’s look at how it works and how you can use it accurately.
1. When do we use ‘not only… but also’?
We use not only… but also to emphasise two complementary aspects of the same subject or situation.
For example:
Not only is YouTube entertaining, but it is also educational.
Here, we are emphasising two positive qualities of YouTube: it is entertaining and educational.
We could simply say that YouTube is entertaining and educational, but the not only… but also construction gives the sentence greater emphasis and creates a more sophisticated structure.
An important point to remember is that the two elements should be complementary and logically consistent. In the examples below, both qualities are positive:
- Not only is the course informative, but it is also highly practical.
- Not only is exercise beneficial for our physical well-being, but it also improves our mental health.
The structure can also emphasise two negative aspects:
Not only have they broken the vase, but they’ve also spilled wine on the carpet.
Both events are undesirable, and the construction highlights the fact that one unfortunate incident has been accompanied by another.
2. Remember to use inversion in the first clause
This is probably the most common mistake students make with this structure.
When not only introduces the first clause, we must use inversion. In other words, we change the usual word order by placing the auxiliary verb before the subject.
Compare:
- Incorrect: Not only YouTube is entertaining, but it is also educational.
- Correct: Not only is YouTube entertaining, but it is also educational.
Notice the position of the verb is. It comes before the subject YouTube.
Here are some more examples:
- Not only is the city expensive, but it is also extremely crowded.
- Not only are these measures ineffective, but they are also costly.
- Not only have we wasted time, but we’ve also spent a considerable amount of money.
The type of inversion depends on the verb tense and the grammatical structure of the sentence.
If you are using the verb to be, you simply place it before the subject:
Not only is the film entertaining, but it is also thought-provoking.
If you are using another verb in the present or past simple, you generally need the auxiliary verb do, does or did:
Not only does investing in renewable energy reduce carbon emissions, but it also creates jobs.
In this example, does comes before the subject investing in renewable energy. The main verb, reduce, remains in its base form.
3. Don’t use inversion in the second clause
Another frequent mistake is to use inversion in both clauses.
Remember that inversion is required after not only, but not after but also.
For example:
Not only does investing in renewable energy reduce carbon emissions, but it also creates jobs.
The second clause follows normal word order: subject (it), auxiliary verb (does), and main verb (create).
The following sentence is incorrect:
Not only does investing in renewable energy reduce carbon emissions, but also does it create jobs.
We don’t need to invert the second clause.
This is an important distinction. Students sometimes remember that inversion is necessary but then apply it to the wrong part of the sentence, or use it in both clauses.
4. You don’t always need to repeat the subject and verb
In some sentences, repeating the subject and verb in the second clause is unnecessary. This is particularly common when the two elements are closely related.
For example:
Not only is exercise good for our physical well-being, but also our mental health.
The second clause does not contain a subject or a verb. We understand that exercise is also good for our mental health.
We could write:
Not only is exercise good for our physical well-being, but it is also good for our mental health.
However, this version repeats information that is already clear from the first clause. The shorter version is more concise and avoids unnecessary repetition.
The same principle applies when the two elements share the same action:
Not only have they broken the vase, but also the mirror.
Here, we don’t need to repeat they have broken because the meaning is perfectly clear.
This is a useful way of making your writing more concise and avoiding unnecessarily repetitive sentences.
5. Make sure you use parallel structures
This is another important point, particularly when using this construction in your writing.
Parallelism means that the two elements connected by not only… but also should follow the same grammatical pattern.
For example, if you use adjectives in the first part, you should use an adjective in the second part:
Not only is YouTube entertaining, but it is also educational.
Both entertaining and educational are adjectives.
Similarly, if you use nouns, you should generally use nouns in both parts:
The course provides not only practical advice but also valuable information.
And if you use verbs, make sure the two parts are grammatically consistent:
Not only does the policy reduce pollution, but it also improves public health.
Notice that both verbs are in the present simple: reduce and improves.
This brings us to another important aspect of parallelism: maintaining consistent verb tenses.
For example:
Not only did the company reduce its prices, but it also improved the quality of its products.
Both actions are in the past simple.
And in the present perfect:
Not only have they introduced new regulations, but they have also invested in renewable energy.
Both actions are in the present perfect.
When constructing sentences with this structure, pay attention to the grammatical form of both elements. They should be balanced and consistent.
6. Where should you place ‘also’?
One final detail worth remembering concerns the position of also.
We do not separate not only in the first clause. However, we can separate but and also in the second clause by placing also after the verb.
For example:
Not only is the city beautiful, but it is also relatively inexpensive.
Or:
Not only have they broken the vase, but they’ve also damaged the furniture.
However, when we omit the repeated subject and verb, also can appear directly before the second element:
Not only have they broken the vase, but also the mirror.
Both patterns are possible. The choice depends on whether you repeat the subject and verb in the second clause.
Summary: Six things to remember
Before using not only… but also in your Cambridge English exam, make sure you remember these six points:
- Use it to emphasise two complementary ideas. The two elements should be logically consistent.
- Use inversion after not only. Remember to place the auxiliary verb before the subject.
- Don’t use inversion after but also. The second clause follows normal word order.
- Avoid unnecessary repetition. You don’t always need to repeat the subject and verb in the second clause.
- Use parallel structures. Make sure the two elements have a consistent grammatical form and, where relevant, matching verb tenses.
- Pay attention to the position of also. It normally comes after the verb when the second clause is complete.
Final advice for your Cambridge English exam
The not only… but also construction is a useful way of making your writing more sophisticated, particularly when you want to emphasise two related arguments or advantages.
For example, in an essay about the benefits of investing in public transport, you could write:
Not only would greater investment in public transport reduce traffic congestion, but it would also help to improve air quality.
This is a natural and effective way of connecting two arguments without simply listing them.
You can use advanced grammatical structures in the B2 First exam as well as in C1 Advanced and C2 Proficiency. The important thing is to use them accurately and appropriately. There is little benefit in attempting a sophisticated construction if you cannot control its grammar.
So, practise creating your own examples, paying particular attention to inversion and parallelism. Once you are comfortable with the structure, it can become a very useful addition to your grammatical repertoire.
For more help with grammar structures like this, check out my Essential Grammar course.