noun
one's younger brother
Humble or formal term for one's own younger brother, often used in letters or formal speech. Contrasts with 舎兄 (one's elder brother).
See also: 舎兄
舎弟は来年大学を卒業します。
My younger brother will graduate from university next year.
noun
sworn younger brother; underling; junior male peer
In yakuza or similar hierarchical groups, refers to a junior member who has sworn loyalty. Also used more broadly for a junior male peer in certain traditional or organizational contexts.
彼は組長の舎弟として、組織の中で重要な役割を担っている。
As the boss's sworn younger brother, he plays an important role in the organization.