Hi Onell --

Yes, it is possible to have "not only" without "but also."

The meaning of the sentence below fits the standard purpose of the not only/but also structure in that it offers one piece of info (the "not only") phrase, and then extends it even further with a second piece of info (the "but also"). The "but also" is usually a tidbit of info that is somewhat surprising when presented in conjunction with the "not only" tidbit.

In this example, the word "actually" is similar to how the word "also" can be used in adding emphasis to the sentence.

In any NO/BA phrase, the "but also" is not the most important element; the "not only" is what sets up the main meaning.

"Today is the best day of my life: Not only did I get a promotion, I was also accepted to Harvard!"

Idioms can be tough, since there's not always a concrete rule, right?

Hope this imprecise explanation shed some light on it for ya.

EssaySnark