What is four prefix?

1. Un-: This prefix means "not," "opposite of," or "lack of." For example, "unhappy" means not happy, "unfair" means opposite of fair, and "uncertain" means lack of certainty.

2. Re-: This prefix means "again" or "back." For example, "revisit" means to visit again, "recheck" means to check again, and "recall" means to call back.

3. Pre-: This prefix means "before" or "prior to." For example, "prepay" means to pay before, "preview" means to view before, and "prelude" means an introductory music piece played before the main event.

4. Post-: This prefix means "after" or "later than." For example, "postpone" means to schedule for later, "postgraduate" means after graduation, and "posthumous" means occurring after death.