Negative Prefixes 

In English, we often create the opposite or negative form of a word by adding a prefix to the beginning. 

Some of the most common ones in English include un-, in-, im-, il-, ir-, and dis-. Each one has its own pattern, depending on the first letter or sound of the root word. 

• Root word: The “core” or “base” of a word that provides its basic meaning. 

• Prefix: A word part added at the beginning of a root word to modify its meaning or create a new word. 

Let’s look at how they work!  

un- 

Used with many adjectives and past participles, especially when no other prefix fits. It works with words beginning with both vowels and consonants. 

• unhappy = not happy 

• unfair = not fair 

• unusual = not usual 

• uncomfortable = not comfortable 

This is the most flexible and frequently used negative prefix. 

in- 

Used with some words starting with consonants and vowels, but not those beginning with i or u (as those usually take il-, im-, or un-). 

• invisible = not visible 

• incomplete = not complete 

• inaccurate = not accurate 

Some words starting with “in” aren’t negative (e.g. involve, invite). 

im- 

Used before words beginning with m or p, for ease of pronunciation. 

• impossible = not possible 

• immature = not mature 

• impatient = not patient 

Think of im- as a variation of in-, adjusted to match the sound of the word. 

il- 

Used before words beginning with i. 

• illegal = not legal 

• illegible = not legible (difficult to read) 

• illogical = not logical 

This is a specialised version of in-, used to maintain smooth pronunciation. 

ir- 

Used before words starting with the r. 

• irregular = not regular 

• irresponsible = not responsible 

• irrelevant = not relevant 

Just like il- and im-, ir- helps the prefix blend naturally with the root word. 

dis- 

Often used to express opposition, reversal, or absence. Common with verbs and some adjectives. 

• disagree = to not agree 

• dislike = to not like 

• dishonest = not honest 

It often creates the opposite meaning or shows something is reversed. 

Summary Table 

Prefix	Use with words that begin with…	Examples
un-	most consonants and vowels	unfair, unknown
in-	many consonants and some vowels (not i or u)	inactive, invisible
im-	m or p	impossible, immature
il-	i	illegal, illegible
ir-	r	irregular, irresponsible
dis-	often used for verbs and adjectives	dislike, disagree, dishonest

Remember: 

• Many negative prefixes follow sound-based patterns (for example, im- before m or p, ir- before r). 

• Not every word starting with un-, in-, im-, il-, ir-, and dis- is negative (for example, understand, imagine, inspire, illuminate, discuss) 

• Some words simply need to be memorised, as not all follow a strict rule. 

• The best way to learn is through exposure and practice (reading, writing, and speaking).