un- 1
a prefix meaning "not," freely used as an English formative, giving negative or opposite force in adjectives and their derivative adverbs and nouns ( unfair; unfairly; unfairness; unfelt; unseen; unfitting; unformed; unheard-of; un-get-at-able ), and less freely used in certain other nouns ( unrest; unemployment ).
[ ME un-, on-, OE; c. D on-, Goth, G un-, ON u-, o-; akin to L in-, Gk an-, a-. See A- 6 , AN- 1 , IN- 3 ]
Syn . See in- 3 .
un- 2
a prefix freely used in English to form verbs expressing a reversal of some action or state, or removal, deprivation, release, etc. ( unbend; uncork; unfasten; etc.), or to intensify the force of a verb already having such a meaning ( unloose ).
[ ME, OE un-, on-; c. Goth and-, D ont-, G ent-; akin to L ante, Gk antí; cf. ANTE-, ANTI- ]
Note . See un- 1 .