"Not only... but also" adds EMPHASIS and surprise to the second element (which surpasses or extends the first); "both... and" connects two elements of EQUAL weight with no special emphasis on either.
NOT ONLY... BUT ALSO: EMPHATIC correlative conjunction. First introduces something already known or sufficient (NOT ONLY), then adds something that SURPASSES, EXTENDS, or SURPRISES (BUT ALSO). "She is not only a great manager but also an inspiring mentor" = being a great manager is already impressive, but she is also an inspiring mentor (the second element ADDS and AMPLIFIES). In formal written English, when NOT ONLY appears at the START of a clause, it triggers INVERSION of subject and auxiliary: "Not only DID she pass the exam, but she also broke the record." (NOT: "Not only she passed...") The inversion is OBLIGATORY in formal English.
Not only did the new platform reduce operational costs by 30 percent, but it also improved the overall customer satisfaction score significantly.
The initiative not only addressed the immediate talent shortage but also established a pipeline for long-term organizational growth.
Not only has she mastered the technical skills required for the role, but she has also demonstrated the leadership qualities needed to grow further.
BOTH... AND (vs NOT ONLY... BUT ALSO): the distinction is not of meaning but of EMPHASIS and STRUCTURE. BOTH... AND is NEUTRAL and INCLUSIVE: joins two elements without giving more weight to either. "She is both a great manager and an inspiring mentor" = both qualities carry equal weight. NOT ONLY... BUT ALSO is EMPHATIC: the first element (NOT ONLY) is already positive or sufficient, but the second element (BUT ALSO) SURPASSES, EXTENDS, or SURPRISES. The obligatory inversion when NOT ONLY begins a clause is a formal feature that BOTH does not share.
The candidate is both technically proficient and culturally aligned with the organization — a rare combination that makes the decision straightforward.
Both the marketing strategy and the product roadmap will need to be revisited given the recent shifts in the competitive landscape.
The solution is both scalable and cost-effective — it addresses the immediate needs without compromising the long-term infrastructure goals.
Common mistake
The two main errors with NOT ONLY... BUT ALSO: (1) FORGETTING THE INVERSION when NOT ONLY begins the clause. "Not only she passed the exam, but she also broke the record" = INCORRECT. Correct form with inversion: "Not only DID she pass the exam, but she also broke the record." The inversion (auxiliary + subject) is OBLIGATORY in formal English when NOT ONLY begins the clause. (2) OMITTING "ALSO." "She is not only smart but brave" = grammatically acceptable in informal English, but in formal English the full form "not only... but ALSO" is preferred. Note: "but also" is sometimes shortened in colloquial speech, but in professional texts it is always included.
Trick to remember it
THE INVERSION AFTER NOT ONLY: when NOT ONLY opens a clause, think of it like a question. In English, questions invert the order: "Did she pass?" With NOT ONLY, the same logic applies: "Not only DID she pass" (not: "Not only she passed"). To avoid confusion: put NOT ONLY in the middle of the sentence when possible: "She not only passed the exam but also broke the record" (NO inversion needed because NOT ONLY is not at the start of the clause). Emphasis rule: NOT ONLY... BUT ALSO = the second element IS MORE IMPRESSIVE. If both elements are equally important = use BOTH... AND.
Quick rule
Not only... but also = emphatic (the second element amplifies or surpasses the first). Both... and = neutral (two equal elements). With NOT ONLY at the start of a clause = obligatory inversion of auxiliary and subject.
Did you know?
The syntactic inversion after NOT ONLY is an example of the linguistic phenomenon called "negative inversion" or "negative fronting" in English. This type of inversion is triggered when certain negative or quasi-negative expressions begin the clause: NOT ONLY, NEVER, RARELY, SELDOM, HARDLY, SCARCELY, NO SOONER... THAN. "Never have I seen such dedication." "Rarely does she make a mistake." "Hardly had he arrived when the meeting started." These constructions are characteristic of literary and formal English and appear frequently in academic, legal, and political texts. They are highly marked in contemporary colloquial English, so using them correctly is a clear signal of advanced command of formal English.
Exercise 1 · Pick the right one
Not only _____ the initiative cut response times in half, but it also generated measurable improvements in customer retention.
Exercise 2 · Pick the right one
The redesigned product is _____ more intuitive for new users _____ significantly easier to maintain for the engineering team.
Exercise 3 · Form the word
Not only... but also = emphatic (the second element amplifies or surpasses the first). Both... and = neutral (two equal elements). With NOT ONLY at the start of a clause = obligatory inversion of auxiliary and subject.
The two main errors with NOT ONLY... BUT ALSO: (1) FORGETTING THE INVERSION when NOT ONLY begins the clause. "Not only she passed the exam, but she also broke the record" = INCORRECT. Correct form with inversion: "Not only DID she pass the exam, but she also broke the record." The inversion (auxiliary + subject) is OBLIGATORY in formal English when NOT ONLY begins the clause. (2) OMITTING "ALSO." "She is not only smart but brave" = grammatically acceptable in informal English, but in formal English the full form "not only... but ALSO" is preferred. Note: "but also" is sometimes shortened in colloquial speech, but in professional texts it is always included.
THE INVERSION AFTER NOT ONLY: when NOT ONLY opens a clause, think of it like a question. In English, questions invert the order: "Did she pass?" With NOT ONLY, the same logic applies: "Not only DID she pass" (not: "Not only she passed"). To avoid confusion: put NOT ONLY in the middle of the sentence when possible: "She not only passed the exam but also broke the record" (NO inversion needed because NOT ONLY is not at the start of the clause). Emphasis rule: NOT ONLY... BUT ALSO = the second element IS MORE IMPRESSIVE. If both elements are equally important = use BOTH... AND.
Bryan López
Founder of SpeakUP Academy