道 (Dào) is the central concept of Daoism (道教, Dàojiào) — 'the Way' — the fundamental principle underlying the universe, as described in the 道德经 (Dàodéjīng) by Laozi.
usage
Also a measure word for questions (一道题), courses of food (一道菜), and long thin things like rays (一道光).
