This running together of the terms upāya and yāna is crucial to understanding the meaning of yāna in Mahāyāna texts, and it has a number of far-reaching consequences that totally transform its usage (compared with early Buddhism). First, yāna refers to the various means (upāya) that are used by the Buddha to bring beings to enlightenment.
Secondly, because these devices are really only modifications of the one truth, yāna also means that one truth or liberation itself.
Thirdly, because this eka-yāna is the same as the Buddha, it can never be limited or defined or even pointed to. Here we enter the paradoxes of Mahāyāna metaphysics. One cannot get at the beginning, middle, or end of this one great vehicle (Aṣṭasāhasrikā-Prajñāpāramitā Sūtra 23); hence in the last analysis, there is no yāna and no one who rides it (Laṅka 135). It is just like space, which contains all forms but itself has no form and can never be got hold of. In typical Mahāyāna style, therefore, we are offered everything and nothing at the same time.
"Yāna." The Concise Oxford Dictionary of World Religions. . Encyclopedia.com. (November 13, 2018). https://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/yana
"Yāna." The Concise Oxford Dictionary of World Religions. . Retrieved November 13, 2018 from Encyclopedia.com: https://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/yana