Nark noun – A person who provides information about another's wrongdoing. Police officer and nark are semantically related. in investigator of crime topic. In some cases you can use "Police officer" instead a noun "Nark".
Police officer noun – A member of a force charged with law enforcement at the local level. Nark and police officer are semantically related. Sometimes you can use "Nark" instead a noun phrase "Police officer".