TOEIC Word Forms: Why Choosing Between "Effective" and "Effectively" Is 13.2% of the Exam

What is a word-form question on the TOEIC?

One where the four options are the same root in different parts of speech — effective, effectively, effectiveness, effect. In eng-test.com’s analysis of 16,214 TOEIC-style Reading questions, 2,140 items turn on that choice, which is 13.2% of the bank and the largest grammar cluster in it.

It is also the hardest. 25.7% of these questions are rated hard and only 23.1% easy — against 6.0% hard for verb form. The difference is that verb form is decided by a trigger word, while part-of-speech choice is decided by the slot: what the sentence structurally needs at that point.

Which suffix signals which part of speech?

English marks part of speech on the end of the word, and the TOEIC relies on it completely. Across every single-word answer in the analysed bank, these are the endings that appear most and what each one reliably signals.

These counts are across all single-word correct answers in the 16,214-question set, not only the word-form items — which is the point. -ate appears 583 times and is almost always a verb; -ly appears 400 times and is almost always an adverb. Two endings alone let you eliminate options in a large share of Part 5.

-ly is the single most reliable signal on the exam. If the blank is not describing a noun, an option ending in -ly is very often the answer; if it is describing a noun, an -ly option is almost never the answer.

How do you decide which form the slot needs?

Look at what sits either side of the blank, not at the meaning. Eight slot patterns cover most of the 2,140 questions, and each one accepts exactly one part of speech.

This is a structural test, which is why a learner with strong vocabulary can still lose these marks. Knowing what effective means does not tell you whether the slot wants effective or effectively — only the words around the blank do.

Which words appear most in these questions?

Adjectives dominate, and they are formal business adjectives rather than everyday ones. These are the words most often correct across the 2,140 word-form and part-of-speech questions.

effective leads at 45 and imperative at 40. Note how many of them end in the suffixes from the table above — effective, comprehensive, informative and innovative are all -ive adjectives, while diligently, promptly, thoroughly and carefully are all -ly adverbs. The list is really the suffix rules wearing different roots.

Several of these are the same formal words that make the finance context the hardest in the bank: substantial, significant and comprehensive all appear in why TOEIC finance questions are the hardest, and the same register problem is at work.

What is inversion, and why does it appear here?

Inversion is when a negative adverb starts the sentence and forces the auxiliary verb in front of the subject: “Not only **has** the company expanded…” rather than “Not only the company has expanded…”. The bank has 47 questions on inversion with negative adverbs, plus 59 on the inverted third conditional.

Inversion is why has, had and does appear among the most common answers in this cluster despite not being adjectives. It is a small group of questions but a completely learnable one — the opening phrase gives the structure away every time.

How should you study word forms?

By suffix first and by word second. Because 25.7% of these items are hard, this is not a cluster to leave to instinct — but because the signal is on the end of the word, it is far more systematic than it looks.

1. 1Learn the twelve endings in the table above. They cover the great majority of single-word answers in the bank.
2. 2For every new word you learn, write all four forms, not one: effective / effectively / effectiveness / effect. The exam will ask for whichever one you did not write down.
3. 3Practise identifying the slot with the options covered. Say “adjective” or “adverb” out loud before you look.
4. 4Do the easier grammar clusters first — verb form is only 6.0% hard against 25.7% here, so it is the cheaper win.
5. 5Drill inside timed items. Part 5 question types and tactics covers how these sit alongside the other Part 5 families, and the free 5-question sample mixes them.

If you are building a vocabulary routine around this, record the forms as a set rather than as separate cards — the techniques that make vocabulary stick explain why a word learned in isolation is the one that fails under time pressure.

How reliable are these figures?

These count eng-test.com’s own bank, not official ETS papers, which are not public. The 2,140 total groups several skill labels that all test part-of-speech choice — adjective choice, adverb choice, noun forms, parts of speech and inversion — so it is a family, not a single label. Read it as “this kind of question” rather than as one official category.

The suffix counts are across all single-word correct answers in the full 16,214-question set, including questions that are not testing word form, because the point of that table is which endings the exam’s vocabulary actually uses. Difficulty ratings are the bank’s own consistent internal scale.

Figures come from a 16,214-question snapshot of the active Reading pool inside eng-test.com’s bank of 20,000+ original items, taken on 10 July 2026 and re-counted on 26 September 2026. eng-test.com is independent and not affiliated with ETS or the official TOEIC test. Methodology: our analysis of 16,214 TOEIC Reading questions.