If something is compulsory, you must do it or accept it, because it is the law or because someone in a position of authority says you must.
mandatory
In East Germany learning Russian was compulsory.
在前东德,俄语是必修课程。
Many companies ask workers to accept voluntary redundancy as opposed to compulsory redundancy.
许多公司要求工人们接受自愿离职,而非强制性下岗。