4.3 Word Forms and Derivation
Key Takeaways
- Word-form items swap one part of speech for another; English marks parts of speech with suffixes, so the ending often reveals whether a word is a noun, verb, adjective, or adverb.
- Common noun suffixes include -tion, -ment, -ity, -ness, and -ance/-ence; common verb suffixes include -ize, -ate, -ify, and -en.
- Common adjective suffixes include -ous, -ful, -ive, -al, -ic, and -able/-ible; most adverbs add -ly to an adjective (quick to quickly).
- Decide the part of speech the slot needs before judging meaning: an adverb modifies a verb or adjective, an adjective modifies a noun, and a noun fills a subject or object slot.
- Watch high-frequency confusions such as economic vs economical, advise (verb) vs advice (noun), and affect (verb) vs effect (noun).
Why Suffixes Are Your Best Clue
Word-form errors are among the most common on the TOEFL ITP, and they are also the most learnable, because English usually marks the part of speech with an ending (suffix). When an underlined word is the wrong class for its slot — a noun where an adjective belongs, or an adjective where an adverb belongs — recognizing the suffix tells you instantly what is wrong and how to fix it.
Quick Answer: First decide what part of speech the slot needs (does it modify a verb? a noun? does it fill a subject or object?). Then check whether the underlined word's suffix matches that class. If the slot needs an adverb but the word ends in an adjective suffix, that word is the error.
The key habit is to judge the slot before the word. Ask: "What kind of word must go here?" An adverb modifies a verb, an adjective, or another adverb (runs quickly, very carefully). An adjective modifies a noun (a careful plan). A noun fills a subject, object, or complement slot (the success of the plan).
This slot-first method protects you from a common mistake: choosing the word that means the right thing but is the wrong class. The test does not punish meaning; it punishes the wrong part of speech. A sentence may use a perfectly sensible idea like economy, but if the slot needs an adjective (economic growth), the noun is still the error. Train yourself to label the slot — verb-modifier, noun-modifier, subject, object — before you even read the underlined word, and the suffix check becomes nearly automatic.
Suffixes by Part of Speech
Learn these high-frequency endings. The suffix is not a perfect rule, but on the TOEFL ITP it is reliable enough to drive most word-form decisions.
| Part of speech | Common suffixes | Original examples |
|---|---|---|
| Noun | -tion, -sion, -ment, -ity, -ness, -ance/-ence, -ist, -ship | creation, decision, agreement, ability, kindness, performance, scientist, leadership |
| Verb | -ize, -ise, -ate, -ify, -en | organize, advertise, activate, clarify, strengthen |
| Adjective | -ous, -ful, -ive, -al, -ic, -able/-ible, -ant/-ent, -less | famous, useful, creative, logical, scientific, comfortable, different, careless |
| Adverb | -ly (added to an adjective) | quickly, carefully, logically, easily |
A practical chain shows how one root shifts class with its suffix:
- noun: His analysis was thorough.
- verb: They will analyze the data.
- adjective: She used an analytical method.
- adverb: He reviewed the figures analytically.
Choosing the Right Form for the Slot
Most word-form errors fall into two patterns:
- Adjective where an adverb is needed. She finished the test quick. The word modifies the verb finished, so it needs the adverb quickly. Test: if the underlined word describes how an action happens, it should usually end in -ly.
- Adjective or verb where a noun is needed. The economical of the country improved. The slot after the and before of is a subject, which needs a noun — economy. Test: if the slot is a subject, object, or follows the, look for a noun suffix.
Common Word-Form Confusions
Some pairs share a root but differ in form and meaning. These appear in error-identification items because choosing the wrong member changes the grammar of the slot:
| Confusion | Distinction | Correct use |
|---|---|---|
| economic vs economical | economic = about the economy; economical = money-saving | economic growth; an economical car |
| advise vs advice | advise = verb; advice = noun | She advised him; good advice |
| affect vs effect | affect = verb (to influence); effect = noun (a result) | Rain affects travel; the effect was clear |
| succeed / success / successful | verb / noun / adjective | They succeeded; great success; a successful trial |
| industrial vs industrious | industrial = about industry; industrious = hardworking | an industrial zone; an industrious student |
Worked Word-Form Example
Item: The new policy had a (A) significant (B) affect on enrollment, and administrators (C) responded by (D) expanding the program.
Scan for word form. Part B, affect, sits after the article a and the adjective significant, so the slot needs a noun — the result of the policy. The noun is effect, not the verb affect. Part B is the error. Part A significant correctly modifies the noun slot, and the verbs responded and expanding in C and D are fine. The fix turns a significant affect into a significant effect.
Match each suffix to the part of speech it most commonly signals.
Match each item on the left with the correct item on the right
In which underlined part is there a grammatical error? 'The researchers (A) carefully (B) measured each sample and recorded the (C) result (D) accurate in a shared log.'
Which sentence chooses the correct word form for the slot?
A word-form item underlines a word that fills the subject slot of the sentence (it follows 'the' and is followed by a verb). What part of speech should that word be?