The Concise Oxford Dictionary of World Religions (2721 page)

na in Mah
y
na texts, and it has a number of far-reaching consequences that totally transform its usage (compared with early Buddhism). First, y
na refers to the various means (up
ya) that are used by the Buddha to bring beings to enlightenment.
Secondly, because these devices are really only modifications of the one truth, y
na also means that one truth or liberation itself.
Thirdly, because this eka-y
na is the same as the Buddha, it can never be limited or defined or even pointed to. Here we enter the paradoxes of Mah
y
na metaphysics. One cannot get at the beginning, middle, or end of this one great vehicle (
A
as
hasrik
-Prajñ
p
ramit
S
tra