Two names, mostly one book. Zhou Yi (周易) is the original core - 64 hexagrams with judgments, a Western Zhou divination text. Yi Jing (易經) is the expanded classic - that core plus the Ten Wings commentaries, canonized as one of the Confucian Thirteen Classics. The difference matters when you read about it, not when you consult it.
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Download free PDFThe Zhou Yi core
The Zhou Yi is the oldest layer: the hexagram figures, the hexagram judgments (卦辭), and the line statements (爻辭). Terse, oracular, practical - a working manual from roughly 1000-750 BCE. When scholars say "Zhou Yi," they usually mean this divination core specifically.
The Yi Jing classic
The Yi Jing is the Zhou Yi plus the Ten Wings - philosophy, cosmology, and commentary added over centuries. As a "Jing" (經, classic), it joined the Confucian canon: the book was no longer just consulted, it was studied, memorized, and quoted by scholars for two millennia. Same skeleton, far more flesh.
Which term to use when
Where this leads
For the core itself, start with I Ching for Beginners; for the commentaries, What Are the Ten Wings?. The glossary defines every term used on this page.
For guidance and self-awareness purposes only. This lesson explains Chinese astrology as a cultural and philosophical framework - what it is, where it came from, and how its vocabulary works. It is not a prediction of your future, a medical or financial opinion, or a substitute for professional advice.