Definitions

1. adverb

not, to an unknown extent, or to any extent; in no way; not at all

“The uninvited guest left early.”

2. prefix

denoting a lack, absence, or negation

“The unemployment rate is rising.”

3. noun

a single unit, especially in computing

“The un is the basic unit of a file system.”

4. interjection

an expression of shock, horror, or disgust

“Un!”