When a word is new, its beginning and ending can help you guess what it means. A prefix or suffix is a clue to test, not a rule to obey. This lesson shows how to use the clue and then check it against the sentence.
It belongs with vocabulary and inference and follows naturally from inferring a familiar word in a new sense.
What can affixes tell you?
Prefixes often change meaning. un-, im-, dis- and il- often mean “not” or “the opposite”. mis- often means “wrongly” and re- often means “again”.
Suffixes often show the word class. -able suggests “can be done”, -ness suggests a noun for a quality, and -ly often makes an adverb. Used together with the root, they let you build a meaning.
How to test a word, step by step
- Split the word into prefix, root and suffix, if it has them.
- Think of the root in a word you know, such as “pass” in impassable.
- Build a meaning from the parts.
- Check the sentence. Does your meaning fit the subject, the tone and the clues around it?
- Reject it if it clashes. A word that only looks like it has an affix should be treated as a whole.
Worked example
After the landslide, the bridge was impassable, so the villagers had to walk to the next town.
Step 1, split: im- + pass + -able.
Step 2, root: “pass” means to go across or through.
Step 3, build: im- means not, -able means able to be done, so “not able to be passed”.
Step 4, check: the villagers “had to walk to the next town”, which shows they could not use the bridge. The meaning fits.
Answer: impassable means cannot be crossed or travelled through.
The mistake to watch for
Mistaken answer: “The detectives slowly unravelled the mystery. Un- means not, so they did not ravel it: they failed to solve it.”
The student trusted the prefix and ignored the sentence. “Slowly” and “the mystery” suggest progress, and in this word un- reverses a tangle, as in untying a knot. Here “unravel” means to untangle or work out.
The correction is to always finish the check in step 4. If the prefix-based meaning makes the sentence strange, the affix is giving a false clue. Also remember words such as “uncle” and “reach”, where the first letters are not prefixes at all.
Check yourself
1. “The teacher found her handwriting illegible.” Use the parts to explain the word.
Show answer
il- means not, and legible comes from a root meaning able to be read. So illegible means cannot be read. It fits a sentence about handwriting.
2. “Many people misinterpreted the notice and arrived a day early.” What does the word mean?
Show answer
mis- means wrongly, interpret means to understand the meaning, and -ed shows past tense. So it means understood wrongly. Arriving a day early confirms it.
3. “The committee will disband after the event.” Is dis- meaning “not” enough? Explain.
Show answer
Not quite. Dis- here means undo or reverse, and “band” means a group. The word means stop existing as a group. “Not band” is unclear, so checking the sentence matters.
Where this leads next
Next, practise reading attitude in speech and writing with identifying a speaker’s attitude from evidence, or try the vocabulary and inference practice set. The writing revision compare view can help you notice when a word choice changes your meaning.
If your guesses at new words are right half the time, a teacher can show you when to trust a prefix and when to reject it. That is part of online one-to-one English as a Second Language tuition.