a. morally or legally constraining or binding
s. required by obligation or compulsion or convention
a. 义务的, 必须的, 强制性的
[法] 有拘束的, 强制的, 必须的
1. Attendance at the meeting is obligatory for all team members.
所有团队成员都必须参加会议。
2. Wearing a uniform is obligatory in this school.
在这所学校穿制服是强制性的。
3. It is obligatory to submit your homework on time.
按时提交作业是必须的。