Duty and Must-have

Duty noun - A charge usually of money collected by the government from people or businesses for public use.

Must-have and duty are semantically related. In some cases you can use "Must-have" instead a noun "Duty".

Must-have noun - Something necessary, indispensable, or unavoidable.

Duty and must-have are semantically related. Sometimes you can use "Duty" instead a noun phrase "Must-have".