非得 (fēi děi): (followed by a verb phrase, then – optionally – 不可, or 不行 etc) must

Mom, do I really have to finish watching this episode of the cartoon right now?

It rained heavily last night and the roads were deeply flooded, so we had to take a long detour to get home.

His illness absolutely requires hospitalization; taking medicine as an outpatient is no longer effective.

This math problem can only be solved by using the formula the teacher taught; I tried other methods and they all failed.

Why do you insist on going grocery shopping today? The supermarket is having a discount tomorrow, and it'll be much cheaper.