un-un- /ʌn/ prefix 
1[in adjectives, adverbs, and nouns] used to show a negative, a lack, or an opposite SYN not: 
unfair unhappy unfortunately uncertainty2[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.
1[in adjectives, adverbs, and nouns] used to show a negative, a lack, or an opposite SYN not: unfair unhappy unfortunately uncertainty2[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.