The systematic and planned extermination of an entire national, racial, political, or ethnic group.

Raphael Lemkin, a Polish-born lawyer, coined the term in 1943, combining the Greek word ‘genos’ (race or tribe) with the Latin word ‘cide’ (to kill). After witnessing the horrors of the Holocaust, Lemkin campaigned to have genocide recognized as a crime under international law, and in December 1948 his efforts gave way to the adoption of the United Nations Convention for the Prevention and Punishment of Genocide, which came into effect in January 1951.

Genocide is a term defined by Article 2 of the Convention on the Prevention and Punishment of the Crime of Genocide (CPPCG) as "any of the following acts committed with intent to destroy, in whole or in part, a national, ethnic, racial or religious group, as such: killing members of the group; causing serious bodily or mental harm to members of the group; deliberately inflicting on the group conditions of life, calculated to bring about its physical destruction in whole or in part; imposing measures intended to prevent births within the group; and forcibly transferring children of the group to another group."

The CPPCG was adopted by the UN General Assembly on 9 December 1948 and came into effect on 12 January 1951 [Resolution 260 (III)]. It contains an internationally-recognized definition of genocide which was incorporated into the national criminal legislation of many countries, and was also adopted by the Rome Statute of the International Criminal Court (Article 2), the treaty that established the International Criminal Court (ICC).

In Prosecutor v. Radislav Krstic [Appeals Chamber-IT-98-33(2004) ICTY 7] paragraphs 8,9,10, and 11 addressed the issue of ‘in whole or in part’ in the definition and found that "the part must be a substantial part of that group. The aim of the Genocide Convention is to prevent the intentional destruction of entire human groups, and the part targeted must be significant enough to have an impact on the group as a whole."