"Genocide" refers to a systematic attempt to kill everyone belonging to entire race or ethnic group. It is based on race hatred. When the term is used, the numbers involved are usually enormous, in the millions, because it is an entire race that is involved. A "massacre" is broader. It refers to killing a large number of people, who are unable to fight back effectively, and are being slaughtered indiscriminately. It usually refers to a single military or similar action, contained in one place and a short time, so it might involve a hundred or a thousand victims. Six people were killed in the "Boston Massacre" of 1770. Several hundred were killed in the "Amritsar Massacre" of 1919. An estimated 1.2 million in the Armenian genocide of 1915-1916, and about 6 million in the Holocaust, the genocide of Jews by the Nazi regime in 1941-1944.