What if We Can’t Agree on the Definition of “Faith”?

Questions about how to navigate a conversation with someone who insists “faith” is not based on proof, how to use apologetics without sounding like you’re avoiding the question being asked, and how to respond to the statement “Certainty is a sin” logically and tactically.

• How do I navigate a conversation with my friend when we can’t agree on what “faith” means? He’s using a dictionary definition that says it’s not based on proof.
• How can I use apologetics without sounding like I’m avoiding answering the question being asked?
• How can I analyze the statement “Certainty is a sin” logically and respond tactically?