TOEIC Link Part 5: Correlative Conjunctions — both…and, either…or, not only…but also

Some TOEIC Link Part 5 questions revolve around correlative conjunctions — conjunctions that work in fixed pairs, like both…and or either…or. The test exploits them in two ways: it shows you one half of the pair and asks you to supply the correct partner, or it gives you the full pair but breaks the parallel structure the pair demands. Both traps are easy to beat once you know the pairs are fixed and the slots on either side must match. This guide covers the pairs you must memorize, the verb-agreement rule that catches people on either…or, and the parallelism discipline that the whole structure depends on.

What a correlative conjunction is

A correlative conjunction is a pair of words that joins two elements and signals the relationship between them. The two halves are a set — each half requires its specific partner and accepts no substitute:

The pairs are not interchangeable. Both…or, either…nor, and not only…but (without also, depending on the test's accepted forms) are all wrong. When Part 5 shows you neither earlier in the sentence and offers or, nor, and, and but as choices, the answer is simply the fixed partner: nor.

Trap 1: supplying the missing partner

The most direct version of the question hides the second half:

The proposal was approved by neither the finance team ___ the legal department. (A) or (B) and (C) nor (D) but

Neither has exactly one partner — nor — so the answer is (C). You do not need to read the rest of the sentence for meaning. Memorizing the five pairs above turns these into instant points. Scan for the first half (both, either, neither, not only, whether) and write down its mandatory partner.

Trap 2: parallel structure across the pair

The harder trap keeps the pair correct but breaks the parallelism between the two slots. Whatever grammatical form follows the first half must also follow the second half. If the first slot holds a verb, so must the second; if the first holds a noun phrase, so must the second.

✗ The candidate was not only qualified but also she had strong references. ✓ The candidate was not only qualified but also well-referenced.

In the wrong version, not only is followed by an adjective (qualified) but but also is followed by a full clause (she had…). The corrected version follows both halves with adjectives. The rule: picture the words right after the first half, and make the words right after the second half the same kind of structure. This is the same balance demanded by ordinary parallel structure — correlatives simply make the requirement explicit by marking both branches.

A quick self-check: read the sentence twice, once using only the first branch and once using only the second branch, dropping the conjunctions. Both readings should be grammatical sentences.

The candidate was qualified. ✓ The candidate was well-referenced. ✓

If one reading breaks, the parallelism is off.

Trap 3: verb agreement after either…or and neither…nor

When either…or or neither…nor joins two subjects, the verb agrees with the nearer subject — the one closest to the verb — not with both.

Neither the manager nor the employees were informed. (plural employees is nearer → plural verb) Neither the employees nor the manager was informed. (singular manager is nearer → singular verb)

This "proximity" rule surprises test-takers who expect a compound subject to always be plural. With and it would be plural (both A and B are), but either/neither pairs defer to the closest noun. When a Part 5 question pairs neither…nor with verb choices, locate the subject immediately before the verb and match it. This is a close cousin of the agreement reasoning in subject–verb agreement with intervening phrases, where the verb must be matched to the right noun rather than the nearest distractor.

Trap 4: placement of the first half

For not only…but also, the first half should sit directly in front of the element it emphasizes, and the second half should sit in front of the parallel element. Misplacement creates an unbalanced sentence even when both halves are present.

✗ The system not only reduces costs but also it improves accuracy. ✓ The system not only reduces costs but also improves accuracy.

Dropping the stray it restores two parallel verb phrases (reduces costs / improves accuracy). Whenever you see a subject pronoun creeping in after but also, suspect a broken parallel.

A decision process for correlative questions

1. Find the first half of the pair (both, either, neither, not only, whether) and recall its mandatory partner. If the blank is the partner, you are done.
2. If the pair is complete, check parallelism: the structures after each half must match. Read each branch alone and confirm both are grammatical.
3. If the pair is either…or or neither…nor joining subjects, agree the verb with the nearer subject.
4. Watch for stray pronouns after the second half that turn a phrase into a clause and break the balance.

Correlative conjunctions are pure pattern recognition once you have the five pairs memorized and the parallelism habit built. They reward preparation directly, which makes them some of the most reliable points on the Part 5 grammar section.