not only... but (also)

Question

Xvtis from Georgia asked about the construction not only....but (also).

Answer

The construction not only....but (also) is called a correlative conjunction. It is used to present two related pieces of information. Both pieces of information are being presented by the writer as surprising or unexpected, with the second one being even more surprising than the first. The first piece of information, which we’ll call [A], comes after not only, and the second piece of information, [B], comes after but (also), like this:  

not only [A] ....but (also) [B]

Below are some sentences with the construction not only [A] ....but (also) [B]. [A] and [B] are underlined. 

1. Lily eats not only string beans but also broccoli.
2. The candidates campaigned not only in Iowa but also in New Hampshire.
3. Not only did Samuel start playing the piano before he could speak, but his mother taught him to compose music at a very early age.

The most important rule to remember about using this construction is that [A] and [B] must be parallel structures, in other words, the same part of speech, as in the examples above. In sentence 1, [A] and [B] are both nouns (string beans and broccoli). In sentence 2 they are both prepositional phrases, and in sentence 3 they are both main clauses. Although you will certainly find examples that do not follow this rule, many grammarians, writing teachers, and writers insist upon this rule, so it is best to follow it, especially in formal writing.

I hope this helps.