What is Genocide of a particular group is called?

The Mongols, Jinghiz Khan a particular ruthless killer among them, devastated large sections of Persia, the Middle East, Eastern Europe, Russia and China-perhaps murdering through the 14-15th Centuries as many as 30 million people (about 13 percent of the world's population). Then, of course, there was slavery which may have accounted for the murder of about 17 million African blacks; and the murder of the Indians of the Americas, another 13 or so million. These are just the most notorious examples, but then there were the less deadly only in their lesser number of victims, such as in the murder of Christians by the Romans, the Christian Crusades, the Aztec sacrifices, the Spanish Inquisition, the witch hunts, the frequent anti-Jewish pogroms throughout Europe, and so on.