compulsory

In many countries, it is compulsory for all citizens to wear seatbelts while in a moving vehicle.

(Chinese) 在许多国家，所有公民在行驶的车辆中都必须系安全带。

The university has made mathematics a compulsory subject for all engineering students.

(Chinese) 大学已将数学列为所有工程系学生的必修课。