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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 → 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 → unhappy). If you add one to a verb, it stays a verb (do → redo). This is the opposite of suffixes, which can change the part of speech (happy → happiness, adjective to noun).
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Explore all 254 English prefixes
Meaning, formation, real audio pronunciation, and examples, organized by category.
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.
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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 → unhappy, still an adjective). A suffix goes at the end and can change the part of speech (happy → 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.
Explore all 254 English prefixes
Meaning, formation, real audio pronunciation, and examples, organized by category.