Guess the Part of Speech from the Suffix: A Fast TOEFL ITP Structure Trick
Guess the part of speech from the suffix in TOEFL ITP Structure and Written Expression: spot nouns, verbs, adjectives, adverbs, the -ly trap, plus a quiz.
Do you freeze when you see an unfamiliar word in a TOEFL® question? Relax: for many grammar questions you don’t need to know what it means. You only need to know one thing: is it a noun, verb, adjective, or adverb?
In TOEFL ITP Section 2 (Structure & Written Expression), many questions test word-class position. The answer choices often share the same root (grow, growth, growing, grown), and the only difference is the ending (suffix). If you know the suffix patterns, you can identify the word class in seconds. (The slides below are in Indonesian, with the English examples.)
Why Suffixes Matter in TOEFL
Look at answer choices like these:
The rapid ___ of the city surprised researchers.
(A) grow (B) growth (C) grows (D) grown
All four share the same basic meaning. The test isn’t checking vocabulary; it’s checking which word class fits that slot. The pattern:
- Look at the words around the blank (before and after).
- Decide which word class is needed.
- Pick the word with the matching suffix.
If word classes still feel fuzzy, start with Parts of Speech 101.
Trick 1: Noun Suffixes for Things and Concepts
Common endings: -tion / -sion, -ment, -ity, -ance / -ence, -ness, -ship, -th.
| Suffix | Examples |
|---|---|
| -tion / -sion | action, pollution, decision |
| -ment | development, agreement |
| -ity | ability, activity |
| -ance / -ence | importance, difference |
| -ness | darkness, awareness |
| -ship | leadership, relationship |
| -th | growth, strength |
Noun positions: after an article (the, a, an), after an adjective, after a preposition (of, in, for), or after a possessive (its, their).
❌ The rapid grow of the city surprised researchers.
✅ The rapid growth of the city surprised researchers.
The pattern The + (adjective) + ___ + of almost always needs a noun. Grow is a verb, so the answer is growth.
Trick 2: Noun Suffixes for People
Common endings: -er, -or, -ist, -ian, -ant / -ent.
| Suffix | Examples |
|---|---|
| -er | teacher, writer |
| -or | actor, inventor, director |
| -ist | scientist, artist |
| -ian | musician, historian |
| -ant / -ent | assistant, resident |
The common trap is swapping the person for the thing or the field.
❌ Thomas Edison was a brilliant invention who held over 1,000 patents.
✅ Thomas Edison was a brilliant inventor who held over 1,000 patents.
The subject is a person (Edison), and who follows. So you need the agent (inventor), not the thing he made (invention). Similar pairs: economist vs economy vs economics, biologist vs biology, photographer vs photography.
Trick 3: Adjective Suffixes
Common endings: -able / -ible, -ive, -al, -ous, -ic, -ful, -less.
| Suffix | Examples |
|---|---|
| -able / -ible | reliable, visible |
| -ive | creative, effective |
| -al | natural, original |
| -ous | dangerous, famous |
| -ic | economic, scientific |
| -ful / -less | powerful, careless |
Adjective positions: before a noun (an effective solution) or after to be and linking verbs (is, seem, become: The plan seems effective).
❌ The team proposed an effect solution to reduce traffic.
✅ The team proposed an effective solution to reduce traffic.
The blank sits right before the noun solution, so it needs an adjective: effective.
Trick 4: Verb Suffixes
Common endings: -ize / -ise, -ate, -ify, -en.
| Suffix | Examples |
|---|---|
| -ize | organize, maximize |
| -ate | activate, stimulate |
| -ify | simplify, clarify |
| -en | shorten, lengthen |
Verb positions: as the main verb after the subject, or after a modal (can, will, must).
❌ Sunlight active vitamin D synthesis in the skin.
✅ Sunlight activates vitamin D synthesis in the skin.
The first sentence has no verb at all. The subject sunlight is singular and the sentence is in the present tense, so the verb is activates.
Note: not every -ate word is a verb. Fortunate and accurate are adjectives, and climate is a noun. Use the word’s position in the sentence to confirm.
Trick 5: The -ly Adverb and Its Trap
Usually, adjective + -ly = adverb:
- quick → quickly
- easy → easily
- exact → exactly
But here’s the trap: noun + -ly = adjective.
- friend → friendly
- cost → costly
- time → timely
- love → lovely
❌ The delegates resolved the conflict in a very friend manner.
✅ The delegates resolved the conflict in a very friendly manner.
Before the noun manner, you need an adjective. Friendly is an adjective, even though it ends in -ly. Since there’s no natural adverb form like friendlily, English uses the phrase in a friendly way/manner.
Suffix Summary
| Word class | Common suffixes | Typical position |
|---|---|---|
| Noun (thing/concept) | -tion, -ment, -ity, -ance, -ness, -ship, -th | After the/a, adjectives, prepositions, its/their |
| Noun (person) | -er, -or, -ist, -ian, -ant | Refers to a person, often followed by who |
| Adjective | -able, -ive, -al, -ous, -ic, -ful | Before a noun, after to be/linking verbs |
| Verb | -ize, -ate, -ify, -en | After the subject or a modal |
| Adverb | adjective + -ly | Modifies verbs, adjectives, or adverbs |
| Trap | noun + -ly (friendly, costly, timely) | Still an adjective |
Quick Quiz
Choose the correct form:
- The (create / creative / creation) of the national park protected many species.
- Marie Curie was a famous (science / scientist / scientific).
- Engineers tried to (simple / simplify / simplicity) the design.
- Repairing the old bridge turned out to be very (cost / costly / costing).
Answers:
- creation. The pattern The ___ of needs a noun.
- scientist. It refers to a person, so you need a person noun.
- simplify. After to (infinitive) you need a verb.
- costly. After very and to be you need an adjective; costly is an adjective despite the -ly.
Train Your Word-Class Reflex
Memorizing suffixes isn’t enough on its own. You need to see these patterns in hundreds of sentences until they’re automatic.
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