Capital punishment, the death penalty, death sentence, or execution is a legal process whereby a person is put to death by the state as a punishment for a crime. Crimes that can result in a death penalty are known as capital crimes or capital offences. The term capital originates from the Latin capitalis, literally "regarding the head" (referring to execution by beheading).

Capital punishment has in the past been practised by most societies (one notable exception being Kievan Rus); currently only 58 nations actively practice it, and 97 countries have abolished it (the remainder have not used it for 10 years or allow it only in exceptional circumstances such as wartime). It is a matter of active controversy in various countries and states, and positions can vary within a single political ideology or cultural region. In the European Union member states, Article 2 of the Charter of Fundamental Rights of the European Union prohibits the use of capital punishment.

Currently Amnesty International considers most countries abolitionist. The UN General Assembly has adopted, in 2007, 2008 and 2010, non-binding resolutions calling for a global moratorium on executions, with a view to eventual abolition. Although many nations have abolished capital punishment, over 60% of the world's population live in countries where executions take place, as the People's Republic of China, India, the United States of America and Indonesia, the four most-populous countries in the world, continue to apply the death penalty (although in India, Indonesia and many US states it is only used rarely). Each of these four nations voted against the General Assembly resolutions.

War is an organized, armed, and often a prolonged conflict that is carried on between states, nations, or other parties typified by extreme aggression, social disruption, and usually high mortality. War should be understood as an actual, intentional and widespread armed conflict between political communities, and therefore is defined as a form of political violence. The set of techniques used by a group to carry out war is known as warfare. An absence of war (and other violence) is usually called peace.

In 2003, Nobel Laureate Richard E. Smalley identified war as the sixth (of ten) biggest problems facing the society of mankind for the next fifty years. In the 1832 treatise On War, Prussian military general and theoretician Carl von Clausewitz defined war as follows: "War is thus an act of force to compel our enemy to do our will."

While some scholars see warfare as an inescapable and integral aspect of human culture, others argue that it is only inevitable under certain socio-cultural or ecological circumstances. Some scholars argue that the practice of war is not linked to any single type of political organization or society. Rather, as discussed by John Keegan in his History of Warfare, war is a universal phenomenon whose form and scope is defined by the society that wages it. Another argument suggests that since there are human societies in which warfare does not exist, humans may not be naturally disposed for warfare, which emerges under particular circumstances. The ever changing technologies and potentials of war extend along a historical continuum. At the one end lies the endemic warfare of the Paleolithic^{[citation needed]} with its stones and clubs, and the naturally limited loss of life associated with the use of such weapons. Found at the other end of this continuum is nuclear warfare, along with the recently developed possible outcome of its use, namely the potential risk of the complete extinction of the human species.