网友记住以下几条即可：

1. police 是一个集合名词，指“警察部门”、“警察机关”、“警方”； 也可以指具体的警察，等于policeman，但人数不能低于两人。所以，可以说two police。

2. 在使用时，尤其是新闻英语，加the 不加the， 均可。

3. police 前有无定冠词举例：

The police are also looking for a second car. 

警方也在寻找另一辆车。

Police say they have arrested twenty people following the disturbances. 

警方说骚乱发生后他们已逮捕了20人。

来自柯林斯词典

4. police 表示具体的“警察”举例：

There were over 100 police on duty. 

有超过百名警察值班。（《牛津中阶英语词典》）

Over 100 police were called in to deal with the riot. 

100多名警察被叫来对付暴乱。（《麦克米伦高阶英语词典》）

Several hundred police were on duty at the demonstration.

在示威游行现场有几百名警察执勤。（《张道真英语用法》）

(1)police 为集合名词，意思“警察部门；警方”不能句具体数词连用。

Police surrounded the courthouse. 警察围在法院大楼四周。

By the time the police arrived the man had fled. 

等警察到达时，那人已逃走了。

Police are still searching for the murder weapon.

警方仍在寻找凶器。

The police were called. 已经报了警。

He was arrested by the police for dangerous driving. 

他因危险驾驶被警察逮捕。

He plans to join the police when he leaves school. 

他打算毕业后去当警察。

A man was arrested by the police and held for questioning. 

一名男子被警方逮捕并拘押讯问。

Get out of the house or I'll call the police . 

滚出这所房子，不然我就叫警察了。

Police suspect a local gang. 

警方怀疑当地的一个不良帮派。 

Hundreds of police in riot gear struggled to control the violence. 

数以百计的警察身披防暴装备，奋力镇压暴乱

(2)作定语后可以与数词/冠词连用two police officers2名警官

Two police officers had a narrow escape when separatists attacked their vehicles.  

分裂主义者袭击他们的车辆时，两名警官死里逃生。

Two police officers arrested him and took him to Kensington police station. 两名警察逮捕了他并把他带到了肯辛顿警察分局。

the police force 警力,警察部队

a police officer 警察，警官

a police station(=building where the police work) 警察局

a police car 警车

a police dog 警犬

(1)a police(错误）

(2)a police officer(正确）

(3)a policeman(正确）

(4)a policewoman(正确）