Taiji

Taiji refers to the primordial, undifferentiated state before the separation of Yin and Yang. The common saying is: 'Taiji gives birth to the Two Modes, the Two Modes give birth to the Four Symbols, and the Four Symbols give birth to the Eight Trigrams.' This describes a process of successive doubling from a unified whole: the Two Modes are Yin and Yang, the Four Symbols are Greater Yin, Lesser Yang, Lesser Yin, and Greater Yang, and a further division yields the Eight Trigrams.

Thus, the Eight Trigrams are not eight parallel things, but the result of three successive binary divisions. Understanding this explains why the lines of a trigram are composed of three strokes, without needing to memorize it separately.