A paramilitary is a force whose function and organization are similar to those of a professional military

Military

A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...

, but which is not considered part of a state's

State (polity)

A state is an organized political community, living under a government. States may be sovereign and may enjoy a monopoly on the legal initiation of force and are not dependent on, or subject to any other power or state. Many states are federated states which participate in a federal union...

 formal armed forces

Armed forces

The armed forces of a country are its government-sponsored defense, fighting forces, and organizations. They exist to further the foreign and domestic policies of their governing body, and to defend that body and the nation it represents from external aggressors. In some countries paramilitary...

.

The term paramilitary is subjective, depending on what is considered similar to a military force, and what status a force is considered to have. The nature of paramilitary forces therefore varies greatly according to the speaker and the context.

For instance, in Northern Ireland

Northern Ireland

Northern Ireland is one of the four countries of the United Kingdom. Situated in the north-east of the island of Ireland, it shares a border with the Republic of Ireland to the south and west...

, paramilitary refers to any illegal armed group with a political purpose, but in Colombia

Colombia

Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

, paramilitary refers only to illegal armed right-wing groups (such as the United Self-Defense Forces of Colombia

United Self-Defense Forces of Colombia

The United Self-Defense Forces of Colombia was created as an umbrella organization of regional far-right...

) that are not in direct opposition to the government, while illegal armed left-wing groups rebelling against the government (such as Revolutionary Armed Forces of Colombia

Revolutionary Armed Forces of Colombia

The Revolutionary Armed Forces of Colombia – People's Army is a Marxist–Leninist revolutionary guerrilla organization based in Colombia which is involved in the ongoing Colombian armed conflict, currently involved in drug dealing and crimes against the civilians..FARC-EP is a peasant army which...

) are referred to as guerrilla

Guerrilla warfare

Guerrilla warfare is a form of irregular warfare and refers to conflicts in which a small group of combatants including, but not limited to, armed civilians use military tactics, such as ambushes, sabotage, raids, the element of surprise, and extraordinary mobility to harass a larger and...

s.
Depending on context, paramilitaries can include:

• Police forces
• Gendarmerie
  Gendarmerie
  A gendarmerie or gendarmery is a military force charged with police duties among civilian populations. Members of such a force are typically called "gendarmes". The Shorter Oxford English Dictionary describes a gendarme as "a soldier who is employed on police duties" and a "gendarmery, -erie" as...
  
  s, e.g.