‘兄弟’ (xiōng dì) literally combines 兄 (xiōng), meaning ‘elder brother’, and 弟 (dì), meaning ‘younger brother’. Together, it refers to brothers collectively—whether two or more, and whether biologically related or not. It emphasizes fraternal kinship and shared upbringing, and is commonly used in family contexts, official documents, and formal speech.

In modern spoken Chinese, especially among young people, ‘兄弟’ frequently serves as an informal, affectionate term of address between close male friends—similar to English ‘bros’ or ‘mates’. This usage conveys camaraderie, loyalty, and mutual support, often appearing in casual conversation, online forums, and pop culture. While traditionally gender-specific, its slang use is overwhelmingly male-oriented, though context may occasionally extend it more broadly.