‘昆弟’ is a formal, literary term meaning ‘brothers’, used especially in classical or written Chinese to refer to male siblings collectively. The character 昆 (kūn) originally meant ‘elder brother’ or ‘together’, and carries connotations of unity and seniority; 弟 (dì) means ‘younger brother’. Together, they form a compound that emphasizes fraternal kinship in a respectful, elevated register—not used in casual speech. It often appears in historical texts, official documents, formal speeches, or poetic contexts where dignity and tradition are valued.

Unlike the everyday word 兄弟 (xiōng dì), which covers both older and younger brothers and is neutral in tone, 昆弟 excludes the eldest sibling (who would be called 兄) and implies equality among younger brothers—or sometimes serves as a respectful collective term for all brothers in formal address. Its usage reflects Confucian ideals of familial harmony and hierarchy, and it may also appear in idioms or fixed expressions such as ‘昆弟之好’ (kūn dì zhī hǎo), meaning ‘fraternal friendship’.