己 jǐ is a pictograph of a coiled, bending line. The oracle-bone and bronze forms show a thread or cord doubled back on itself in a zigzag, the early picture of something wound and knotted. That original sense survives in the related character 纪 jì (a thread, a record, a discipline), where the silk radical 糸 is added back. The bare shape 己 was borrowed early as a loan-graph for the spoken word meaning "oneself," and the self-meaning so completely took over that the thread sense now lives only in its descendants. 己 is its own radical, the head of a small family that includes 已 and 巳.

Three senses branch from the borrowed self:

1. Oneself, self. The reflexive "self" of a person: 自己 zìjǐ (oneself), 自我 zìwǒ (the ego, the self), 知己 zhījǐ (a bosom friend, one who truly knows you).
2. Personal, one's own, private. What belongs to the self as opposed to others: 己见 jǐjiàn (one's own view), 利己 lìjǐ (self-interest), 克己 kèjǐ (self-restraint).
3. The sixth Heavenly Stem. In the cycle of ten 天干 tiāngān used to count days and years, 己 is the sixth, paired in the calendar with the earth phase.

The thread running through every sense is the turn inward. Whether the self is the grammatical reflexive, the private opinion held against the crowd, or the personal will that must be curbed, 己 is the point a person comes back to: the doubled-back line that always returns to where it started.

When 己 points at the self that wants and clings, Chinese ethics treats it as the thing to be governed. Confucius gave the tradition its keyword: 克己 kèjǐ, to master the self. His phrase 克己复礼 ("subdue the self and return to ritual propriety") makes self-restraint the gate to virtue. To curb the personal will so the wider order can hold is, in this view, the whole of moral cultivation.

The same 己 supplies the vocabulary of selfishness and selflessness. 利己 lìjǐ is acting for one's own benefit; its opposite, 舍己 shějǐ, is setting the self aside. Between them sits 己见 jǐjiàn, one's own view, prized when it is independent and warned against when it is stubborn. In every case the self of 己 is a center of gravity that ethics asks a person to hold loosely, neither erased nor indulged.

Apart from "self," 己 has a second life as the sixth of the ten 天干 tiāngān, the Heavenly Stems: 甲 乙 丙 丁 戊 己 庚 辛 壬 癸. Cycled against the twelve Earthly Branches, the stems generate the sixty-term count that has numbered days and years across the long sweep of the Chinese calendar. In the five-phase scheme each pair of stems takes a phase, and 己 belongs to earth (土), the yin earth to 戊's yang. A year such as 己亥 pairs the stem 己 with a branch to name one slot in the sixty-year round.

This second reading is the same character and the same sound, jǐ, third tone. Context tells the two apart at once: among pronouns and ethics it is "self," among 甲乙丙丁 it is the calendrical stem.

See the single coiled thread of 己 bending back on itself and returning to its start. That doubling-back is the self: every meaning of 己 is the point a person comes home to. It is oneself plainly (自己), the friend who knows that self (知己), the private opinion held against the room (己见), and the self that ethics asks you to curb (克己) or even give up (舍己为人).

For the look-alikes, hold the mouth in mind: 开口己 the open-mouthed self, 半口已 the half-open already, 闭口巳 the shut-mouthed branch. The opening stroke on the left rises higher with each one, from fully open in 己, to halfway in 已, to sealed shut in 巳.