It's derived from Medieval French, which in turn was derived from Latin (politia - civil administration), and was further derived from ancient Greek (Polis - city).
It stands for the word "cartridge"
Police
Woman Police Constable
MPO stand for Military Police Officers.
The Police Department is usually abbreviated PD.
La police is the french word for police.
Of course they are - Do you think police have to stand on trains?
It stands for criminal investigating police officer.
International Police
Australian Federal Police
Royal Canadian Mounted Police
The word police is predominantly a noun. Police can also be a verb.