Prefixes
B1 · IntermediateWord FormationHappy → unhappy, possible → impossible, agree → disagree — a prefix changes meaning, almost never word class.
What you'll learn
- A prefix attaches to the front of a word and changes its meaning, usually without changing its word class: happy (adjective) → unhappy (still an adjective)
- English has several negative prefixes — un-, dis-, non-, and in- (which becomes im- before b/m/p, il- before l, ir- before r) — and which one attaches to a given word isn't predictable; it has to be learned per word
- Other prefixes add meaning beyond negation: re- (again), over- (too much), under- (too little), pre- (before), mis- (wrongly)
- Unlike suffixes, prefixes almost never change a word's part of speech
What a prefix does
A prefix is a small piece added to the beginning of a word. It changes the word's meaning — often to its opposite — but it almost always keeps the same part of speech: happy and unhappy are both adjectives.
Four negative prefixes, one meaning
un-, dis-, non-, and in- all mean 'not', but English doesn't let you choose freely — each word has one correct negative prefix that simply has to be learned. in- itself has three spelling variants depending on the sound that follows: im- before b/m/p (impossible, immature), il- before l (illegal), and ir- before r (irregular).
Prefixes that add other meanings
Not every prefix is negative. re- means 'again', over- means 'too much', under- means 'too little', pre- means 'before', and mis- means 'wrongly' or 'badly'.
Real English
Watch out
un- is common, but 'possible' specifically takes im- — each word's negative prefix has to be learned, not assumed.
'responsible' takes ir-, not un- — there's no shortcut rule for which negative prefix a word uses.
Real life — A misunderstanding at work
"I think you misread my email — I said the deadline was preponed, not postponed."
"Oh no, that's so unfortunate. I already overslept this morning and now this."
"It's not impossible to still make it, but we'll need to redo the schedule quickly."
"Agreed. Let's not disagree about whose fault it was and just fix it."
Practice
Exercise 1 · Choose the correct negative form
Choose the correct negative form: possible → ___
Exercise 2 · Choose the correct negative form
Choose the correct negative form: legal → ___
Exercise 3 · Choose the correct negative form
Choose the correct negative form: responsible → ___
Exercise 4 · Choose the correct negative form
Choose the correct negative form: happy → ___
Exercise 5 · Choose the correct negative form
Choose the correct negative form: agree → ___
Exercise 6 · Choose the correct prefix
Which prefix means 'again'?
Exercise 7 · Choose the correct prefix
Which prefix means 'too much'?
Exercise 8 · Choose the correct prefix
Which prefix means 'wrongly' or 'badly'?
Exercise 9 · Complete the word
Add a prefix to make the opposite: This information is correct → This information is ___correct.
Exercise 10 · Complete the word
Add the prefix meaning 'before': The teacher gave a ___view of the lesson. (view = re-, over-, or pre-?)
Exercise 11 · Sort the words into groups
0 / 8 sorted
Quick challenge
Five quick questions to check what stuck.
Question 1 / 5
Score: 0/0
Choose the correct negative form: regular → ___
You learned
- A prefix attaches to the front of a word and changes its meaning, almost never its word class.
- English has four negative prefixes — un-, dis-, non-, in-/im-/il-/ir- — and the correct one has to be learned per word.
- Other prefixes add meaning: re- (again), over- (too much), under- (too little), pre- (before), mis- (wrongly).
- There's no shortcut rule for which negative prefix a given word takes.
Related grammar lessons
Suffixes
Learn how suffixes attach to the end of a word and usually change its word class — noun-forming suffixes like -tion/-ment/-ness, adjective-forming suffixes like -ful/-able, verb-forming suffixes like -ize/-ify, and the adverb-forming -ly.
Compound Words
Learn how English combines two or more words into a single unit with a new, more specific meaning — written as one word, two words, or hyphenated, with no reliable spelling rule to predict which.
Changing Word Classes
An overview of how English words shift between word classes — mainly through suffixes, while prefixes usually change meaning without changing class — and a preview of the more surprising mechanism covered in its own lesson: conversion, where a word changes class with no visible change at all.
Conversion / Zero Derivation
Learn about conversion (zero derivation) — English's most surprising way of changing a word's class, where a word shifts to a new part of speech with absolutely no prefix, suffix, or any change in form at all.