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English Prefixes: What They Are, Types, and a List With Examples
A prefix goes before the word and changes its meaning, not its part of speech: happy becomes unhappy is still an adjective.
Written by Bryan López, Profesor de inglés · Updated
An English prefix is a group of letters added to the start of a word to change its meaning, without changing its part of speech: happy (adjective) becomes unhappy (still an adjective), just with the opposite meaning. Learning the most common prefixes lets you guess the meaning of thousands of new words without memorizing them one by one.
The 4 types of English prefixes
A prefix never changes the word's part of speech
This is the most important rule: if you add a prefix to an adjective, it stays an adjective (happy becomes unhappy). If you add one to a verb, it stays a verb (do becomes redo). This is the opposite of suffixes, which can change the part of speech (happy becomes happiness, adjective to noun).
Negative prefixes aren't interchangeable
You can't just pick any negative prefix at random: each word has its own, and there's no 100% fixed rule for which one. You say unhappy but impossible, not "unpossible." The only reliable way to learn it is by seeing each word with its correct prefix, not just memorizing the rule alone.
How to use prefixes to guess the meaning of new words
When you come across an unfamiliar word, split the prefix from the root: if you see "misunderstand," identify "mis-" (wrongly, incorrectly) + "understand" = to understand incorrectly. This trick works on thousands of academic and technical English words without memorizing all of them.
Explore all 254 English prefixes
Meaning, formation, real audio pronunciation, and examples, organized by category.
A longer list of prefixes with meaning
In-, im-, il-, and ir-: one prefix, four spellings
The negative prefix in- changes its spelling to match the first letter of the root. Before b, m, and p it becomes im-: impossible, immature, imbalance. Before l it becomes il-: illegal, illogical. Before r it becomes ir-: irregular, irresponsible. In other cases it stays in-: incorrect, inactive. This is not an arbitrary rule, it makes the word easier to pronounce.
Hyphens with prefixes
Most prefixes attach directly to the word without a hyphen: unhappy, redo, preview. A hyphen appears in some cases: before a capital letter (anti-American, pre-Columbian), with the prefixes ex- and self- (ex-wife, self-confidence), and when a double vowel would look confusing (re-enter, co-operate in some styles). When in doubt, check a dictionary, because the rules vary.
Practice: guess the meaning
- Unbelievable: not able to be believed
- Rewrite: to write again
- Misspell: to spell wrongly
- Overcooked: cooked too much
- Multilingual: speaking many languages
Wrong negative prefix
Incorrect
It is unpossible to finish today.
Correct
It is impossible to finish today.
Frequently asked questions
What is a prefix in English?
It's a group of letters added to the start of a word to change its meaning, without changing its part of speech. For example, happy becomes unhappy, and both are still adjectives.
What are the most common English prefixes?
The most common are un-, in-, im-, dis-, and non- (negation), re- and de- (reversal), pre- and over- (position and time), and mono-, bi-, and micro- (number and size).
What's the difference between a prefix and a suffix?
A prefix goes at the start of the word and never changes its part of speech (happy becomes unhappy, still an adjective). A suffix goes at the end and can change the part of speech (happy becomes happiness, adjective to noun).
How do I know which negative prefix to use?
There's no 100% fixed rule: it depends on the specific word (unhappy but impossible, not "unpossible"). It's best to learn each word with its correct prefix rather than just memorizing the general rule.
Why is it useful to learn English prefixes?
It lets you guess the meaning of new words without looking them up: if you know "mis-" means "wrongly" or "incorrectly," you understand "misunderstand" without ever having seen it before.
How many prefixes does English have?
There are hundreds of prefixes, but a group of about 20-30 covers the vast majority of words you'll see day to day: un-, re-, dis-, in-, pre-, over-, under-, mis-, and mono-/bi-/tri- among the most frequent.
Does un- always mean not?
No. Un- can also show reversal of an action: undo means to reverse something, untie means to loosen a knot. It is important to check the root verb or adjective to see which meaning applies.
Are prefixes the same in other languages?
Many come from Latin and Greek, so you will find similar prefixes in Spanish: pre-, re-, sub-, inter-, multi-. This helps Spanish speakers a lot when they meet formal English vocabulary.
What is the difference between un- and in-?
Both can mean not, but they go with different words and you usually learn each word with its prefix: unhappy, unusual, but incorrect, invisible. Un- is more common with everyday Germanic words, and in- with words from Latin.
Explore all 254 English prefixes
Meaning, formation, real audio pronunciation, and examples, organized by category.
Keep learning
- English Suffixes: What They Are, Types, and a List With ExamplesA suffix goes at the end of the word and can change its part of speech: happy (adjective) becomes happiness (noun).
- False Cognates in English and Spanish: What They Are, With ExamplesA false cognate is a word that looks like a word in the other language but means something completely different, like embarrassed and embarazada.
- Flashcards to Learn English: How to Use Them So They Actually WorkFlashcards only work if you use spaced repetition: reviewing everything at once doesn't help, you need to review right before you forget.