“Not only” is similar to “both,” but it can be used for more than two things. It’s also similar to “in addition.” The second or third thing mentioned after “not only” is sometimes the thing that the writer wants you to think of as being more important.
1. A horse is not only a beautiful animal, it’s also a useful animal that can do a lot of work.
(This sentence underscores the importance of a horse’s usefulness.)
2. Dogs are not only good at protecting your home, they’re also excellent companions.
3. A college education is not only good for your personal development, it’s also important if you want to get a good job.
4. Not only is Mount Rushmore an important national landmark, it’s also located in a good place for camping.
5. Military intervention is not only ineffective in settling differences between countries, it’s also expensive and it results in the needless deaths of civilians.
6. Reading is not only relaxing, it’s also a very inexpensive activity.