Lesson 4 of 41 in the Test Ninjas TOEFL course: Complete the Words, Reading. Most gaps in Complete the Words test a word you already know.
Test Ninjas Research · Updated October 1, 2026
Lesson at a glance
Detail
This lesson
Module
Complete the Words (Reading)
English focus
Derivational suffixes and prefixes (-tion, -ment, -age, -ary, -ible, -ture, -ly, -ward, un-, im-) and reading word class from a word's position
Task skill
Choosing the ending the slot needs: class from position, family member from meaning, grammar ending from agreement, confirmed by the blank count
Time
About 50 minutes
Access
Included in the TOEFL plan
What this lesson teaches
Most gaps in Complete the Words test a word you already know. The hard part is its form. decide, decision, decisive and decisively are one word family: they share a stem, but each does a different job in a sentence.
In this lesson you read the job a gap needs from its position, build the right family member with a suffix or a prefix, and use the number of blanks to confirm your choice.
By the end of the lesson, you can
Say which class of word a gap needs (noun, verb, adjective, adverb or a small word) from the words on each side of it.
Build the right member of a word family with common suffixes (‑tion, ‑ment, ‑age, ‑ture, ‑able/‑ible, ‑ary, ‑ly, ‑ward) and the prefixes un‑, in‑, im‑, il‑ and ir‑, and spell ‑ible and ‑ly endings correctly.
In Complete the Words, check the class, the meaning and any grammar ending, then use the blank count to reject a family member of the wrong length.
What’s inside
Around the 3 teaching cycles below, the lesson opens with a quick check and closes with applied practice, a Check and a debrief. How every course lesson is built.
Teaching cycles in lesson 4
Cycle
Focus
What it teaches
Drills
Cycle 1
English
Reading word class from the slot
8
Cycle 2
English
Suffixes and prefixes that build word families
8
Cycle 3
Task skill
Choosing the ending the slot needs
7
Word bank
The 10 words and phrases this lesson teaches. They come from the real course questions you practice on in the Apply step, so you meet each one again in context.
merely adverb
only; just; nothing more than
The workshop is merely an introduction; the full course starts in March.
Goes with:
merely a first step
Word family:
mere (adjective): a mere ten minutes
organic matter noun collocation
material from living things, such as plants or food waste
Food waste is organic matter, so the dining hall now sends it to be composted.
Goes with:
rich in organic matter
Word family:
organism (noun): a living thing; organ (noun); organically (adverb)
consume verb
to use up energy, fuel, time or food
Video calls consume a lot of battery, so bring a charger.
Goes with:
consume energy / time
Word family:
consumption (noun); consumer (noun)
exhausted adjective
used up completely; also, extremely tired
The old mine closed once its copper was exhausted. The adjective also means extremely tired: after three exams, Arjun was completely exhausted.