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Prefixes That Mean Not
A small group of prefixes appears in an enormous number of English words. The most common of all are the prefixes that mean not or opposite of. Learn these and you can instantly understand the opposite of hundreds of words you already know. In this lesson you will master the negative prefixes and learn when to use each one.
The most common negative prefixes
| Prefix | Meaning | Examples |
|---|---|---|
| un- | not, opposite of | unhappy, unfair, unlock |
| dis- | not, opposite of, apart | disagree, dishonest, disappear |
| non- | not, without | nonfiction, nonstop, nonsense |
| in- | not | incorrect, invisible, incomplete |
| mis- | wrongly, badly | misspell, misunderstand, mislead |
The prefix un- is the most common prefix in English. It can mean “not” (unkind) or it can reverse an action (untie, unpack).
The in- family: in-, im-, il-, ir-
The prefix in- meaning “not” changes its spelling depending on the first letter of the base word. This makes the word easier to say.
- Before b, m or p, it becomes im-: impossible, imbalance, immature.
- Before l, it becomes il-: illegal, illogical, illegible.
- Before r, it becomes ir-: irregular, irresponsible, irrelevant.
- Most other times, it stays in-: inactive, inaccurate, incapable.
Watch the double letters
Because the prefix keeps all its letters, you often get a double letter: il + legal = illegal, ir + regular = irregular, mis + spell = misspell. Many spelling mistakes happen when people drop one of these letters.
A tricky one: in- does not always mean not
The prefix in- can also mean “in” or “into”, as in include, inhale and insert. And some words like inflammable actually mean “easily set on fire”, not “not flammable”. This is why context and a dictionary matter.
Choosing the right prefix
There is no perfect rule for knowing whether a word takes un-, dis- or in-. Your ear and your reading experience help a lot. You say unhappy, not dishappy, and dishonest, not unhonest. When unsure, check a dictionary.
Example
Read this sentence from a science report: The results were inconclusive, so the team decided to repeat the experiment.
- in- means “not”.
- conclusive means “leading to a clear conclusion or answer”.
- So inconclusive means “not leading to a clear answer”. That explains why the team repeated the experiment.
Example from social studies
The treaty was nonbinding. Non- means “not”, and binding means “must be obeyed”, so the countries did not legally have to follow it.
Mis- means wrongly
Notice that mis- is slightly different from the others. It does not mean “not”; it means “wrongly” or “badly”. To misread is to read incorrectly. To mislead someone is to lead them in the wrong direction, often by giving false information.
Using negative prefixes in your writing
Negative prefixes can make your writing more concise. Instead of The instructions were not clear, you can write The instructions were unclear. Instead of That is not possible, write That is impossible. Be careful not to stack negatives, though: a sentence like It is not unlikely that it will rain is grammatically correct but makes readers work hard to understand that it probably will rain.
Key takeaways
- Un-, dis-, non- and in- usually mean “not” or “the opposite of”.
- In- changes to im-, il- or ir- before certain letters.
- Keep both letters when a prefix creates a double letter, as in misspell.
- Mis- means “wrongly”, and in- can sometimes mean “into”, so check context.
Practice
Add the correct negative prefix and write the meaning: 1. legal, 2. possible, 3. agree, 4. responsible, 5. understand.
Answers: 1 illegal (not allowed by law). 2 impossible (not able to happen). 3 disagree (not agree). 4 irresponsible (not acting responsibly). 5 misunderstand (understand wrongly).