Ascertain (verb)

1. To find out or determine with certainty, especially through investigation or research.
2. To make sure of the accuracy or truth of something.
3. To establish or determine the existence, fact, or truth of something.

Origin:

From the middle english word 'ascerten' meaning to find out or discover.

Examples:

1. She tried to ascertain the cause of the problem.
2. The detective worked to ascertain the identity of the thief.
3. We must ascertain the facts before making a decision.
4. The scientist tried to ascertain the effectiveness of the new drug.
5. The company wanted to ascertain the customer's satisfaction with the product.