What the meaning of Yin and Yang 阴阳？

Yin and Yang are a generalization of the attributes of the opposing sides of certain interrelated things or phenomena in nature. As the saying goes, "Yin and Yang mean dividing one into two." The original meaning of Yin and Yang was simple, referring to the direction of sunlight: facing the sunlight is Yang, and being away from the sunlight is Yin. Later, Yin and Yang no longer specifically referred to the direction of sunlight, but were extended to abstract concepts that summarize the two sides of things and phenomena with opposing attributes in nature.

The theory of Yin and Yang holds that all interrelated and opposing things or phenomena in the universe, or the two opposing aspects within the same thing, can be summarized and analyzed in terms of their respective attributes using Yin and Yang. Generally speaking, Yang represents the aspect of things with attributes such as movement, activity, and strength, including movement, strength, activity, excitement, positivity, brightness, invisibility, function, ascent, exposure, lightness, heat, growth, and life activities. Yin represents the aspect of things with attributes such as stillness, inactivity, and softness, including stillness, softness, inactivity, inhibition, negativity, darkness, tangibility, materiality, descent, internality, heaviness, coldness, reduction, and the physical body.

Of course, the Yin and Yang attributes of things are not absolute but relative. Under certain conditions, Yin can be transformed into Yang, and Yang can also be transformed into Yin; moreover, Yin and Yang can each be further divided into Yin and Yang. For example, daytime is Yang and night is Yin. In the daytime, the morning is Yang within Yang, and the afternoon is Yin within Yang; in the night, the first half of the night is Yin within Yin, and the second half of the night is Yang within Yin. This view reflects the infinite divisibility of things.