A more thorough explanation:

Term: UN-
Definition: A prefix that means "not" or "contrary to".
Examples:

1. Unassignable - not able to be assigned
2. Unconstitutional - against the constitution

The prefix UN- is used to indicate the opposite or absence of a particular quality or condition. For example, unassignable means that something cannot be assigned, while unconstitutional means that something goes against the constitution. These examples illustrate how the prefix UN- can be used to create words that convey a negative or opposite meaning.