Actually only the full-blooded, long-haired bull of the species Bos grunniens truly carries the name
yak. The female is called nak by Sherpas or dri by Tibetans. In the Langtang area most yaks are actually crossbreeds with local cows or Tibetan bulls, which the
Sherpas call lang and Nepali call khirkoo. A nak-lang or yak-cow crossbreed is a dzopkyo if its male and a dzum if it is female. Just to make things complicated,
the Nepali word for dzum is chanri.
By the way: according to legend the Langtang valley has been discovered by a lama following a runaway bull. Hence the name –
lang is Tibetan for bull and dhang means 'to follow'.