police是集合名词，表示警察(泛指)，本身具有复数含义。(就和people一样)
policeman 警察 复数policemen
policewoman 女警 复数policewomen
相关介绍
The two policemen were joined by another policeman also carrying a pistol.
另一名持枪警察和那两名警察会合了。
There were 2,250 policemen on duty in and around the stadium
在体育场内及周边有2,250名警察在值勤。
Policemen and policewomen work at a police station.
男女警员在警察局工作。
Two policewomen are directing traffic at the crossing.
两名警花在十字路口指挥交通。
