un- /ʌn/ BrE AmE prefix
[ Sense 1: Language: Old English ]
[ Sense 2: Language: Old English ; Origin: un- , on- , from and- 'against' ]
1 . [in adjectives, adverbs, and nouns] used to show a negative, a lack, or an opposite SYN not :
unfair
unhappy
unfortunately
uncertainty
2 . [in verbs] used to show an opposite of a particular action:
to undress (=to take your clothes off)
Have you unpacked yet (=taken your things out of your suitcase) ?
I heard Lila unlock the front door.