discipline/ 'dɪsɪplɪn /

1.noun [of children] [ pupils] 
纪律

2.noun [u] 
(self-control) 约束

3.noun [c] 
(branch of knowledge) 学科

4.vt.
to discipline o.s. (to do sth) (train) 训练自己(做某事)

5.vt.
(punish) 惩处