What are 5 examples of words that their own antonyms?

You're looking for auto-antonyms, also known as contronyms or self-antonyms. These are words that have opposite meanings depending on context. Here are 5 examples:

1. Sanction:

* To sanction something can mean to approve it.

* It can also mean to punish or disapprove of it.

2. Fast:

* To fast means to abstain from food.

* A fast car is one that moves very quickly.

3. Cleave:

* To cleave can mean to adhere or stick together.

* It can also mean to split or separate.

4. Dust:

* To dust something is to remove dust.

* Dust can also refer to the fine powder itself.

5. Oversight:

* Oversight can mean a supervision or care.

* It can also mean an error or mistake.

These are just a few examples, and there are many more words in the English language that have opposite meanings depending on context.