The original meaning of li (理) was the texture of jade; later it was extended to contain three meanings: 1) the physical forms or proprieties of things, such as length, size, shape, tensile strength, weight, and color; 2) the universal laws followed by all things and beings; and 3) the original source or ontological existence of things. The last two meanings are similar to those of Dao. Scholars of the Song and Ming dynasties were particularly interested in describing and explaining the philosophy known as li (理), and considered it as the highest realm, giving rise to the School of Principle which dominated academic thought in the period from the Song to the Ming dynasties.
Nothing happens at random; each follows its own li (laws). (Wang Bi: A Brief Exposition of The Book of Changes)
Everything exists according to its objective law but all things must follow the common li (law). (Writings of the Cheng Brothers)