弟

Originally depicts a wooden stick bound with cords or straps, later interpreted as tying things in order or sequence.

From this idea of sequence/order, it came to denote younger sibling, as in birth order.

Over time, specialized to mean younger brother or by extension junior, follower, disciple.

The sense of “order, sequence” was later separated into 第.

Semantic range:

- younger brother;

- junior, subordinate, pupil, disciple;

- metaphorically, “those who follow in order” (e.g. later generations).

형제 (兄弟) — brothers, siblings

남동생/아우 (弟) — younger brother

제자 (弟子) — disciple, student

사제 (師弟) — teacher and pupil relationship

우애 (友愛/兄弟之愛) — brotherly affection

In Confucian ethics, 弟 is integral to the virtue 悌 (제, brotherly respect), one of the Five Cardinal Relationships (오륜, 五倫). It emphasizes filial piety between elder and younger siblings, extending to respect for elders in general.

In Buddhism, 師弟 (master–disciple) is a common compound, where 弟 highlights the humility and obedience of a learner toward a spiritual teacher.

Thus, 弟 carries not only the sense of kinship but also a broader moral and spiritual meaning: respect, humility, and proper order in human relations.