This lesson introduces the origin of the concepts of Yin and Yang by etymology, the basic attributes and characteristics in philosophy, the application in Chinese daily life and in the study of TCM (Traditional Chinese Medicine). It also distinguishes Yin-Yang from masculine, feminine, the genders of nouns in different languages i.e. Spanish, French etc. This lesson further explains the origin concepts of mutual rooting Yin-Yang and Root disease and Brand disease by etymology. It proves that learning TCM in Chinese language can help international students understand both in knowledge and skills deeper from the root.