✅ Mastering Word Families: Avoiding Parts of Speech Traps on TOEIC Part 5

Think you know the word “success”?
Great — but what about “succeed,” “successful,” or “successfully”?

If you don’t know which to use in a sentence, you’re walking straight into one of TOEIC’s favourite grammar traps.

Let’s break down this essential Part 5 topic — and show you how to get it right every time.

💥 Why TOEIC Tests Word Families So Often

TOEIC Part 5 isn’t just about vocabulary. It’s about function — how words fit into the sentence grammatically.

That’s why TOEIC loves to test:

  • Nouns vs. verbs

  • Adjectives vs. adverbs

  • Words that look or sound similar but play different roles

It’s a quick way to check whether you’re reading for meaning or structure — and most test-takers fail here because they don’t fully understand parts of speech.

🧪 Sample TOEIC Part 5 Question

The marketing team’s latest campaign was a huge ___ for the company.

A) succeed
B) success
C) successful
D) successfully

✅ Correct answer: B) success

Why? The blank needs a noun (something the campaign was).
“Success” = noun.
The others are different parts of speech:

  • “succeed” = verb

  • “successful” = adjective

  • “successfully” = adverb

🔄 Common Word Family Traps on TOEIC

TOEIC often gives you four answers that belong to the same word family but serve different functions. Here are some classic examples:

  • effect (noun) vs affect (verb)

  • efficient (adj) vs efficiency (noun)

  • applicant (noun) vs apply (verb) vs applicable (adj)

  • decision (noun) vs decide (verb) vs decisive (adj)

  • performance (noun) vs perform (verb) vs performer (noun)

These are not vocabulary questions — they’re grammar-in-disguise.

🎯 How to Choose the Right Word Form

Step 1: Read the whole sentence, not just the blank.

TOEIC often gives grammar clues before and after the blank.

Step 2: Ask: What part of speech is missing?

  • Is the word describing a noun? → You need an adjective
    The new policy was extremely ___. → “effective”

  • Is the word describing a verb? → You need an adverb
    The team worked ___ under pressure. → “efficiently”

  • Is the word doing the action? → You need a verb
    They will ___ for the visa. → “apply”

  • Is the word the subject or object? → You need a noun
    She showed great ___ in the interview. → “confidence”

⚠️ Common Signals TOEIC Uses

  • Articles (“a,” “the”) → likely followed by a noun

  • “To” + verb → base verb form

  • “Be” + adjective → describes a state

  • “Was done ___” → likely needs an adverb

  • “One of the most ___” → superlative adjective

If you train your eye to notice these patterns, you can often eliminate 2–3 options without knowing the full meaning.

🧠 TOEIC Isn’t Testing Vocabulary — It’s Testing Your Grammar Awareness

This is a mindset shift.

When you see “decision / decide / decisive / decisively” — don’t ask what they mean.
Ask how they function in the sentence.

And in TOEIC Part 5, that difference is everything.

✅ Final Tip: Build Word Families into Your Daily Study

Make it a habit to:

  • Learn nouns, verbs, adjectives, and adverbs together

  • Test yourself with real TOEIC-style blanks

  • Watch for patterns that show what part of speech is missing

The faster you connect form to function, the faster your TOEIC score climbs.

🔍 Hidden FAQ – Word Families & Parts of Speech (TOEIC) Q1: What is a word family in English grammar? A: A word family is a group of words that share the same root but have different forms, like “decide” (verb), “decision” (noun), “decisive” (adjective), and “decisively” (adverb). Q2: Why does TOEIC test word families so often? A: Because they reveal whether you understand how words function in a sentence, not just their meaning. It’s one of the fastest ways TOEIC checks your grammar skills. Q3: How do I know which form to use in a sentence? A: Look at the grammar around the blank. If it’s after an article (“a,” “the”), it’s likely a noun. If it follows “will” or “to,” it’s probably a verb. Clues are everywhere. Q4: What’s the difference between “effect” and “affect”? A: “Effect” is usually a noun (a result), while “affect” is a verb (to influence). TOEIC loves to test this pair because the words sound similar but have different roles. Q5: What part of speech is tested the most on TOEIC? A: TOEIC frequently tests adjective/adverb confusion — for example: “efficient” vs “efficiently.” If a word is modifying a verb, you usually need an adverb. Q6: Can’t I just choose the word that “sounds right”? A: That’s risky. TOEIC often makes all the answer choices sound natural. You need to understand sentence structure, not just rely on feeling. Q7: What’s a good way to study word families for TOEIC? A: Group them in sets. For example, for “apply,” study “applicant,” “application,” “applicable,” and “applied.” Then practise with example sentences. Q8: How do I know if I need a verb or a noun in the blank? A: Ask: “What is the subject doing?” If the blank is the action, it’s a verb. If the blank names a thing or idea, it’s a noun. Grammar clues are key.