Negative Prefixes

A negative prefix gives a word the opposite meaning. The base word itself does not change.

• un- is the most common: unhappy, unfair, unreliable
• in- is used with many other adjectives: incorrect, invisible, informal
• in- becomes im- before m and p: immature, impossible, impatient
• in- becomes il- before l: illegal, illogical
• in- becomes ir- before r: irregular, irrelevant
• dis- is common with verbs and some adjectives: disagree, dislike, dishonest

Keep both letters when they meet: im + mature = immature, ir + responsible = irresponsible. These spelling changes happen only with in-, not with un-: unlucky, unrealistic. There is no simple rule for choosing un- or in-, so learn each word together with its prefix.