un-

¹un-

prefix
\ˌən, often ˈən before ˈ-stressed syllable\

Definition of UN-

1

: not : in-, non- —in adjectives formed from adjectives <unambitious> <unskilled> or participles <undressed>, in nouns formed from nouns <unavailability>, and rarely in verbs formed from verbs <unbe> —sometimes in words that have a meaning that merely negates that of the base word and are thereby distinguished from words that prefix in- or a variant of it (as im-) to the same base word and have a meaning positively opposite to that of the base word <unartistic> <unmoral>

2

: opposite of : contrary to —in adjectives formed from adjectives <unconstitutional> <ungraceful> <unmannered> or participles <unbelieving> and in nouns formed from nouns <unrest>

Origin of UN-

Middle English, from Old English; akin to Old High German un- un-, Latin in-, Greek a-, an-, Old English ne not — more at no