The traditional denotation of gen(艮) of the hexagram Bound in ”Yi Jing” is ”gaze”, and the extended meaning is ”stillness”, keeping the gaze still. However, this paper considers that the denotation of gen(艮) possibly should be ”invisible”, and the extended meaning ”stillness” means that keeping the gaze still because ”invisible”. All the six lines on the hexagram Bound have the meaning of restraint. The explanations in Yi Chuan during the Warring States period became more diverse; it had other more meanings such as timely restraining, purity and sincerity of cultivation, completion and beginning of natural law in the Ming Dynasty. Thereafter, ”Zhouyi” had become a classic which literati were generally familiar with. No one aspiring literatus didn't construct and develop their own ideas by Zhouyi. As far as the meaning of stillness of gen(艮) is concerned, Metaphysician rests only in ”nothing”; Buddhist rests only in ”emptiness”; Taoist rests only in ”vitality”; Neo-Confucianist rests only in ”reason”. It was very spectacular that famous experts came forth one after another. Annotation of classics fully reflected the pulsation of an ideological trend of the era and various aspects.