A dzo (Tibetan མཛོ་ mdzo) is a hybrid between the yak and domestic cattle. The word dzo technically refers to a male hybrid, while a female is known as a dzomo or zhom. Alternative Romanizations of the Tibetan names include dzho, zho and zo. In Mongolian it is called khainag (хайнаг). There is also the English language portmanteau term of yakow; a combination of the words yak and cow, though this is rarely used.Dzomo are fertile (or, fecund) while dzo are sterile.