婚姻 (hūn yīn) refers specifically to the legal and social institution of marriage — not just the wedding ceremony, but the ongoing marital relationship and its societal framework. The character 婚 (hūn) originally meant 'to marry' or 'wedding', while 姻 (yīn) historically referred to marital ties between families, especially through the wife’s side; together, they form a compound emphasizing marriage as a formal, binding union recognized by family and society.

This word is formal and neutral in register, commonly used in discussions about law, sociology, family life, or personal status (e.g., 'marital status' = 婚姻状况). It appears frequently in official documents, news reports, and academic contexts — unlike colloquial alternatives like 结婚 (jié hūn), which emphasizes the act of getting married. 婚姻 carries no inherent emotional connotation; it describes the institution itself, whether harmonious or troubled.