A prefix is a group of letters added to the beginning of a word to form a new word with a different meaning.
In English, one way to make negative statements (as opposed to affirmative statements) is by adding negative prefixes to nouns, adjectives and verbs.

When a negative prefix is added to a word, the newly-formed word means the opposite of the root word, or ‘wrong’/‘bad’/’erroneous’. For example, ‘impolite’ means ‘not polite’, ‘misbehaviour’ means ‘bad behaviour’.

Here are some examples of commonly-used negative prefixes.

NEGATIVE PREFIXES IN ENGLISH

DIS-DE-MIS-UN-
disable
disagree
discontinue
disobey
disqualify
dissatisfy
deactivate
decompose
decontaminate
deflect
demotivate
depopulate
misbehave
misinform
misjudge
misquote
misspell
mistrust
unable
unavoidable
unfit
unfortunate
unnecessary
unpopular
IM-IN-IL-IR-
imbalance
immature
immobile
immoral
imperfect
impolite
inaccurate
inactive
incompetent
indecent
inexact
insecure
illegal
illegible
illegitimate
illicit
illiterate
illogical
irrational
irregular
irreconcilable
irrelevant
irresistable
irresponsible
A-ANTI-NON-EX-
acellular
achromatic
amoral
apolitical
asexual
asymmetric
antibiotic
antibody
anticlimax
anticoagulant
antiseptic
antispam
nonconformist
nonessentiel
nonexistent
nonpartisan
nonrestrictive
nonsense
exclude
exfoliate
exstipulate
ex-member
ex-president
ex-pupil