Essence-Function (體用, Chinese pinyin: tǐ yòng, Korean: che-yong), also called Substance and Function, is a key concept in Chinese philosophy and other Far-Eastern philosophies. Essence is Absolute Reality, the fundamental "cause" or origin, while Function is relative or concrete reality, the concrete manifestation of Essence. Ti and yong do not represent two separate things, such as Absolute Reality and Concrete Reality. They are always two, flexibly-viewed aspects of a single thing.