War is a state of armed conflict between states, governments, societies and informal paramilitary groups, such as mercenaries, insurgents and militias. It is generally characterized by extreme violence, aggression, destruction, and mortality, using regular or irregular military forces. Warfare refers to the common activities and characteristics of types of war, or of wars in general. Total war is warfare that is not restricted to purely legitimate military targets, and can result in massive civilian or other non-combatant suffering and casualties.
The scholarly study of war is sometimes called polemology ( POL-ə-MOL-ə-jee), from the Greek polemos, meaning "war", and -logy, meaning "the study of".
While some scholars see war as a universal and ancestral aspect of human nature, others argue it is a result of specific socio-cultural or ecological circumstances.