One of the first things you’d learn in any Intro to Buddhism course is that most Buddhists alive today are part of the Mahāyāna tradition, in which one aspires to be a bodhisattva (and eventually become a buddha). Mahāyāna is the majority tradition because it’s the one practised in Japan, Korea, most of Vietnam, and China including Taiwan and Tibet. (Tibetans sometimes refer to their tradition as “Vajrayāna”, but they know that that’s still a form of Mahāyāna; there are no non-Mahāyāna Vajrayānists.) The name “Mahāyāna” (translated as “Great Vehicle”) is not in dispute; everybody agrees that that’s the preferred term. That part is easy.

Now here’s a question: what do you call all the other Buddhists?

Your typical intro Buddhism course gets around that question pretty easily, because there’s a simple answer if you’re exclusively talking about Buddhists today, in the modern era. As of about 1850, basically all the non-Mahāyāna Buddhists in the world identified as part of the Theravāda tradition, practised throughout Sri Lanka and mainland Southeast Asia. The only Buddhists who might identify as something else are more recent modernist Buddhists of one stripe or another – hippyish Western Buddhists who don’t want to be pinned down to specifics, or perhaps B.R. Ambedkar’s Navayāna – and they understand they’re doing something new and a little weird. (“Navayāna” means “new yāna”.) In general, it’s pretty reasonable to say that the Buddhism existing in the past thousand years or so has been divided into the two traditions of Mahāyāna and Theravāda.

But go back before that, and things look very different.