Q: What is the correct usage of “not only… but also”? Is “also” necessary here or is it an also-ran?
A: We wouldn’t call “also” an also-ran here, though it’s not always necessary.
There are three ways of dealing with the conjunctive phrases “not only” and “but also,” and all three are perfectly good English.
(1) Use both phrases in their entirety: “He’s not only a doctor but also a lawyer.”
(2) Drop “also”: “He’s not only a doctor but a lawyer.”
(3) Use “as well” instead of “also”: “He’s not only a doctor but a lawyer as well.”
Many people believe that it’s incorrect to drop “also” from a “not only … but also” construction. This isn’t true. Examples 1 and 3 are more formal than example 2, but all are correct.
Which is better? The decision is up to you, as Bryan A. Garner writes in Garner’s Modern American Usage (3rd ed.).
“It’s merely a matter of euphony and formality: let your ear and your sense of natural idiom help you decide in a given sentence,” he writes.
But no matter which style you choose—formal or casual—the elements that you’re joining should be parallel constructions.
In the best writing, what follows “not only” is similar in construction to what follows “but also” or “but.”
For example, if there’s no verb after the first conjunctive phrase (“not only”), there shouldn’t be a verb after the second (“but also”).
Or if there’s a preposition after the first conjunctive phrase, there should be another after the second. Keep the parts parallel. Here’s what we mean:
Parallel: “He attended not only medical school but law school.” Not parallel: “He attended not only medical school but went to law school.”
Parallel: “He went not only to medical school but also to law school.” …Not parallel: “He went not only to medical school but also law school.”
One other point. “Not only” and “but also” can be used with the parts of a compound subject, as in “Not only his son but also his daughter went to boarding school.”
Sometimes, however, the choice of a verb with such a compound subject isn’t that obvious. What if one part of the compound is singular and one is plural?
As Pat writes in her book Woe Is I (3rd ed.), “If the part nearer the verb is singular, the verb is singular,” as in “Not only the chairs but also the table was sold.”
And “If the part nearer the verb is plural, the verb is plural,” as in “Not only the table but also the chairs were sold.”
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