Zhen is one of the eight trigrams (bagua) of the Yijing. It is composed of a single yang line beneath two broken yin lines, and its attribute is Thunder, the Arousing, associated with sudden movement, shock, and the quickening force that stirs things into action. In the family symbolism it is the Eldest Son, the first yang line to appear, and its polarity is yang. Its associated element is Wood, and in the Later Heaven arrangement of the bagua its direction is due east, the place of sunrise and spring. Each of the eight trigrams combines with another to form the sixty-four hexagrams of the Yijing. These are the conventions of the Chinese cosmological and divinatory tradition, in which Zhen, the thunder that breaks the stillness, marks the rousing of new life.
The family member and attribute scheme used throughout the eight trigrams, Zhen among them, is drawn from the Shuogua zhuan, the Explanation of the Trigrams, a commentary appended to the Yijing as one of the Ten Wings; tradition credits it to Confucius, but modern scholarship does not accept that attribution, and manuscript evidence places its compilation toward the end of the Warring States period or the start of the Han, later than the core text it explains. In the Earlier Heaven or Fu Xi arrangement, an older and more static ordering than the Later Heaven sequence used for compass direction above, Zhen stands in the northeast rather than the east.
Sources Fathoming the Cosmos and Ordering the World: The Yijing (I Ching, or Classic of Changes) and Its Evolution in ChinaRichard J. Smith with The I Ching, or Book of ChangesRichard Wilhelm (trans.); Cary F. Baynes (English trans.), The Five "Confucian" ClassicsMichael Nylan