若其后直接跟动词要用动名词
He forbids smoking during office hours. 他禁止上班时间抽烟。
The headmaster has forbidden singing in the corridors. 校长禁止在走廊里唱歌。
若其后先接宾语再跟动词则要用不定式
I forbid him to go there again. 我不准他再去那儿。
The teacher forbids the students to read such books. 老师不准学生看那样的书。
比较下面两句
They forbad swimming in the river. 他们不准在这河里游泳。
They forbad people to swim in the river. 他们不准人们在这河里游泳。
