Six negative prefixes

• un- — broadly "not" (unhappy, unable, unkind)
• in- / im- / il- / ir- — Latin origin, attaches to Latinate roots (invalid, immobile, illegal, irregular)
• dis- — "apart from, not" (disagree, disconnect)
• non- — neutral negation (non-profit, non-fiction)
• mis- — "wrongly" (misunderstand, misuse)
• a- / an- — Greek "without" (atypical, amoral, anaerobic)

Choosing the right one

Generally, Latinate root → in-/im-/il-/ir-, Germanic root → un-.

| Adjective | Negation | Why | | --- | --- | --- | | patient (Latin) | impatient | Latin root takes in-/im- | | kind (Germanic) | unkind | Germanic root takes un- | | moral (Latin) | amoral ≠ immoral | They mean different things! |

amoral = without moral judgment; immoral = morally wrong. Don't confuse them.