a body of persons making up such a department,trained in methods of law enforcement and crime prevention and detection and given the authority to maintain the peace,safety,and order of the community

• 组成这样一个部门的一群人，他们被专门训练来掌握执行法律和防止并侦破犯罪行为的方法，被授予维护一个社区的和平、安全和秩序的职权