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.