Ji

Ji is the sixth of the ten Heavenly Stems (tiangan). Its element is Earth and its polarity is yin, so Ji is glossed as yin Earth, likened in tradition to soft soil, garden earth, or a field, receptive and nurturing where the yang Earth of the fifth stem is the mountain. As one of the ten stems it pairs with the twelve Earthly Branches to build the sexagenary cycle of sixty used to number years, months, days, and double-hours. Each of the five phases appears among the stems once as yang and once as yin, and Ji carries the yin aspect of the central Earth phase. These are the conventions of the Chinese calendrical and cosmological tradition, drawn on in the almanac and in the four-pillars art of fate calculation.

Ji is the sixth Heavenly Stem, paired with Wu under the Earth phase but carrying the Yin polarity, likened to tilled or garden soil, receptive and nurturing, in contrast to Wu's mountain. As an even-numbered stem, Ji combines only with the six Yin Earthly Branches, Ox, Rabbit, Snake, Goat, Rooster and Pig, within the sixty-term sexagenary cycle. In four pillars (BaZi) astrology a Ji day master is read as adaptable and quietly supportive, good at absorbing and refining what other elements bring into a chart, echoing Earth's role in the five-phase (Wu Xing) system as the phase that receives Fire's ash and yields Metal in turn. The stem also carries an ordinal use, marking the sixth position in traditional Chinese enumerated sequences, the equivalent of an F in a Western A-to-J list, a convention still occasionally seen in Chinese legal and contractual documents for labelling parties to an agreement.

Every stem has a partner among the other nine, and the five pairings, called the combinations of the heavenly stems, are fixed: each stem combines with the one five places away from it. Ji pairs with Jia, and the tradition holds that a combined pair takes on a phase of its own distinct from either stem's native phase. The pairing is used in almanac work and in fate calculation, where a combination in a chart is read as a binding between the two positions that carry it.

The ten stems are older than the sexagenary cycle they now form half of. On the Shang oracle bones of the second millennium BCE they name the ten days of the xun, the Shang week, and Shang kings are known to history by posthumous names built on them, so a stem was a unit of the working calendar before it was a term of cosmological art. The five-phase and yin-yang readings attached to the stems are later, systematised under the Han, and the atlas records the two layers as two layers.

Ji is yin Earth, the cultivated soil against the mountain of Wu, and it is the sixth of the ten. Because the stems run in phase order, Wood, Fire, Earth, Metal and Water, each phase taking a yang stem then a yin one, the position of a stem in the ten determines its phase and polarity together, and the list can be reconstructed from the order alone.

The stem's own attributes here are Earth and yin polarity. Those two facts fix its place in the run of ten, since the stems proceed through the five phases in generation order taking the yang member first and the yin member second, and they fix how it is read wherever it appears, in the year, the month, the day or the double hour of a Four Pillars chart.

Sources Chinese Mathematical Astrology: Reaching Out to the StarsHo Peng Yoke with The Chinese Sexagenary Cycle and the Ritual Origins of the CalendarAdam Smith