Negative prefixes

We can add a prefix to some words to make the opposite meaning.

Some negative prefixes are: un-, il-, -im-, ir-, in-, dis-.

• Il- is often used with adjectives beginning with 'l'.
• Im- is often used with adjectives beginning with 'p' or 'm'.
• Ir- is often used with adjectives beginning with 'r'.

Examples:

• unfair, untidy, unable, unusual, unpleasant, unpredictable.
• illegal, illogical, illiterate, illegible.
• immature, impatient, impolite.
• irregular, irrelevant, irresistible, irresponsible, irrational.
• incomplete, informal, incorrect, indecent, insecure, indirect.
• dishonest, dislike, disagree, disappear, disobey, disadvantage, disorganized.

This is one of the best webpages I've found for you to practise. It allows you to choose the ones you want to check according to frequency or the kind of prefix you want to practise.