What does the suffix UN mean?

The suffix "UN" generally means "not" or "the opposite of". It's used to create the opposite meaning of a word.

Here are some examples:

* Happy vs Unhappy

* Tied vs Untied

* Certain vs Uncertain

* Usual vs Unusual

* Real vs Unreal

It's important to note that "UN" is not always used to directly negate a word. Sometimes it can create a more nuanced meaning, like in the word "unprecedented" which means "never before seen" rather than simply "not precedent".