Word Forms & Common Error Repair

Level B2–C2 · noun/verb/adjective/adverb forms; final review

◎What you'll master

Recognise the four main word forms — noun, verb, adjective, adverb — from their typical suffixes.
Choose the right form for the slot: adjective before a noun, adverb to modify a verb or adjective, noun as subject/object, verb as the predicate.
Build complete word families (decide / decision / decisive / decisively).
Separate the tricky pairs, especially economic vs economical, and form -ly adverbs cleanly.
Run a final error repair across the whole course: agreement, tense, articles, prepositions, and word form.

1The four word forms

Most English roots grow a whole family of related words. The same idea appears as a noun (a thing), a verb (an action), an adjective (describes a noun), or an adverb (describes a verb, adjective, or another adverb). Picking the wrong member of the family is one of the most common — and most visible — errors at B2–C2.

noun: a decision · verb: to decide · adjective: a decisive leader · adverb: act decisively

2Choose the form the slot needs

Ask what job the word does in the sentence, then fit the matching form. The grammar of the slot — not the meaning alone — decides the ending.

Adjective before a noun

a successful plan (not a success plan)

Adverb to modify a verb or adjective

She argued persuasively. · a remarkably clear answer

Noun as subject or object

Their decision surprised us. (subject)

Verb as the predicate

They decided quickly. (the action of the clause)

⚠ Watch out — don't let one form do another's job: She spoke very persuasive. → She spoke very persuasively. (an adverb modifies the verb spoke).

3Suffix clues — read the ending

Endings are your fastest signal for which form a word is. They are strong hints, not iron rules.

Form	Typical suffixes	Examples
Noun	-tion, -ment, -ness, -ity, -ance/-ence, -er	decision, movement, happiness, ability, importance, teacher
Verb	-ise/-ize, -ify, -en, -ate	economise, clarify, strengthen, activate
Adjective	-ful, -less, -ous, -ive, -al, -able/-ible, -ent/-ant	useful, harmless, famous, active, natural, reliable, different, pleasant
Adverb	usually -ly	quickly, clearly, decisively

Suffix shortcuts

-tion / -ment / -ness / -ity almost always mark a noun; -ise/-ize, -ify, -en, -ate usually mark a verb; -ous / -ive / -ful / -able mark an adjective; and a word ending in -ly is most often the adverb of the matching adjective (careful → carefully).

4Word families in full

Learn roots as complete sets — noun, verb, adjective, adverb across a single root. When one slot needs a form you don't know, the family gives it to you.

Noun	Verb	Adjective	Adverb
decision	decide	decisive	decisively
success	succeed	successful	successfully
economy	economise	economic / economical	economically
analysis	analyse	analytical	analytically
production	produce	productive	productively

Spelling shifts inside a family

decide → decision · analyse → analysis · succeed → success — the spelling often changes, so store each form, not just the pattern.

5Tricky pairs: economic vs economical, and clean -ly

A few roots split into two adjectives with different meanings. The classic pair is economic vs economical.

Word	Meaning	Example
economic	relating to the economy or economics	the country's economic growth
economical	money-saving, thrifty, not wasteful	an economical little car

⚠ Watch out — economic ≠ economical: an economic car that saves fuel → an economical car; economical policy of the government → economic policy. And build -ly adverbs cleanly — happy → happily, true → truly, public → publicly — not truely or publically.

6Final error-repair review

This is the last lesson, so the checklist below pulls together the mistakes that cost the most marks across the whole course. Read every sentence against all five.

Check	Wrong	Right
Subject–verb agreement	Each of the plans have merit	Each of the plans has merit
Verb tense	I have seen him yesterday	I saw him yesterday
Articles	She is a honest person	She is an honest person
Prepositions	They arrived to the airport	They arrived at the airport
Word form	Her decide was final	Her decision was final

Your capstone habit

After you write anything, do one slow pass asking only: Does the verb agree? Is the tense right? Are the articles correct? Are the prepositions idiomatic? Is every word in the right form?

Practice — 15 questions with instant feedback

0 / 15 correct

Question 1

They made a quick (decide → noun).

Question 2

His new plan was very (success → adjective).

Question 3

The samples were ______ analysed in the lab.

Question 4

To cut costs, the family had to (economy → verb) on fuel.

Question 5

Her argument was very (persuade → adjective).

Question 6

It's an ______ car — it barely uses any fuel.

Question 7

The whole team worked (produce → adverb) all week.

Question 8

The government unveiled a new (economy → adjective) policy.

Question 9

She handled the crisis ______ and calmly.

Question 10

His (analyse → noun) of the data was thorough.

Question 11

Against all odds, they completed the mission (success → adverb).

Question 12

A good researcher needs an ______ mind and steady patience.

Question 13

Although the report ran to forty pages, its (conclude → noun) was clear and convincing.

Question 14

Faced with a tight deadline, the committee acted (decide → adverb), approving the budget within the hour.

Question 15

Because the new machinery proved so ______, the factory doubled its output while cutting costs.

✎Fix the Error

Each sentence has one mistake in the underlined word. Type the correction and check.

1.Her decide to resign shocked everyone.

2.Each of the students have submitted an essay.

3.She is a honest and reliable colleague.

4.The delegates arrived to the conference an hour late.

5.I have finished the report yesterday afternoon.