民警的英文：
policeman

The policeman figured the features of the criminal.
这个警察描述了这个罪犯的特征。

a policeman's beat
警察的巡逻路线

The robber was shot dead by the policeman.
那强盗被警察击毙了。

The policeman caught the thief.
警察逮住了小偷。

The thief ran slap into a policeman.
那贼与警察撞了一个满怀。