Word formation
Negative prefixes
Prefixes like
in-, un- and dis-
can be added to some adjectives, adverbs, verbs and nouns to give them a negative
meaning.
  - Improving your performance with drugs is unfair.
- We're used to seeing athletes, cyclists and
    swimmers disqualified.
- They unrealistically thought that
    they would finish the project on time.
- His insincerity made him very unpopular.
Here are more common examples of words with these prefixes:
In-
  inactive, inadvisable,
    inappropriate, incapable,
    inefficient, inexperienced
Un-
  unauthorized, unable,
    unacceptable, unbearable,
    unbelievable, undetectable,
    unexpected, unhealthy,
    unnecessary, unofficial,
    unpopular, unpredictable,
    unreasonable, unrepeatable,
    unsafe, unsuccessful
Dis-
  disagree, disappear,
    disappoint, disapprove,
    dishonest, disqualified
Also, the prefixes il-, im-
  and ir- can be used in this way. Often, they combine
  like this:
  - il- before adjectives and adverbs that start
    with l: illegal
- im- before adjectives and adverbs that start
    with b, m or p:
    impossible
- ir- before adjectives and adverbs that start
    with r: irresponsible
Here are more common examples of words with these prefixes:
Il-
  illegal, illegible,
    illegitimate, illicit,
    illiterate, illogical
Im-
  imbalance, immobile,
  immodest, immoral,
  immortal, impatient,
  imperfect, impolite,
  impossible, impractical,
  improbable
Ir-
  irrational, irregular,
  irrelevant, irresistible,
  irresponsible, irreversible