This is the 95th most frequent Czech word.
policie
Police.
Here, 'policie' is used as the subject of the sentence, referring to the law enforcement organization.
Policie dorazila na místo činu.
The police arrived at the crime scene.
In this context, 'policii' (a form of 'policie') is used as an object in the sentence. It represents the organization contacted for assistance.
Lidé zavolali na policii, když slyšeli podezřelé zvuky.
People called the police when they heard suspicious sounds.
Here, 'v policii' refers to within the institution or organization of the police, indicating the profession or workplace.