Within the depth-psychology corpus, the trigram occupies a foundational structural position in the literature surrounding the I Ching and its psychological applications. The term designates one of the eight three-line figures — composed of broken (yin) and unbroken (yang) lines — whose pairing into hexagrams constitutes the oracular and cosmological grammar of the Book of Changes. Richard Wilhelm’s translations and commentaries establish the primary lexicon: each trigram is assigned elemental, directional, familial, and psychological attributes (Chen as arousing movement, Li as clinging luminosity, K’an as abysmal danger, K’un as receptive earth), and these attributes function as a symbolic vocabulary for understanding psychic states, relational dynamics, and phases of transformation. The Taoist I Ching tradition, represented by Liu I-ming via Cleary, extends this to a hermeneutic method — reading the lower trigram as subject and the upper as object — making the trigram a diagnostic lens for situational self-knowledge. Wang Bi’s classical commentary deploys trigrams as markers of positional ethics within hexagram structure, linking line-placement to virtue and vice. Across all sources, a persistent tension exists between the trigram as cosmological symbol and as pragmatic interpretive unit, a tension that depth-psychological readings have consistently exploited to bridge Chinese correlative cosmology and Western introspective analysis.