Constabulary may have several definitions.

• A civil, non-paramilitary police force consisting of police officers called constables. This is the usual definition in Britain, in which all county police forces once bore the title (and some still do).

• A large civil police force organized and trained along military lines, which may contain paramilitary elements. This is the usual definition in places outside of Great Britain (e.g. Royal Irish Constabulary, Royal Ulster Constabulary, Royal Newfoundland Constabulary, Royal Canadian Mounted Police, Pennsylvania Constabulary etc.). These were based on the French Gendarmerie, originally consisting of military personnel seconded to or recruited directly to the constabulary or military veterans and later became all civilian forces after they were well established.

• A military or para-military type force consisting of soldiers trained for police duties. These were mostly established by the United States in the several countries it had protective status over (e.g. Philippine Constabulary, United States Constabulary in West Germany after World War Two, Nicaraguan National Guard, Panama National Guard). These forces also performed military functions by maintaining "mobile forces" of organised units. In Europe such forces are called Gendarmeries or (in Italy) Carabinieri.