Definition of "un-" in English

prefix

1. (added to adjectives or past participles) not

   • un- + educated → uneducated (“not educated”)

2. (added to nouns) lack of

   • un- + conformity → unconformity (“lack of conformity”)

3. (added to nouns) contrary to traditional norms; unconventional

   • un- + conference → unconference

prefix

1. (added to verbs) the inverse of a specified action

   • un- + dress → undress (“to take one's clothes off”)
   • un- + lock → unlock (“to undo the locking of”)

2. (added to nouns to form verbs) deprive of, release from, free from, remove from, extract from

   • un- + cage → uncage (“to release from a cage”)
   • un- + tangle → untangle (“to remove the tangling of”)

3. (rare) intensifying a verb that already suggests opposition or removal

   • un- + loosen → unloosen
   • un- + decipher → undecipher
   • un- + thaw → unthaw

prefix

1. (chemistry) Used for the digit one to form systematic element names of elements whose existence has been predicted, and which have not yet been given a trivial name.

   • un- (“1”) + bi- (“2”) + un- (“1”) + -ium (element suffix) → unbiunium (“element 121”)

2. Used to form large numbers as the first in the sequence.

   • un- + decillion (“10³³”) → undecillion (“10³⁶”)
   • un- + vigintillion (“10⁶³”) → unvigintillion (“10⁶⁶”)