宣战 (xuānzhàn) literally means 'to proclaim war' — 宣 (xuān) means 'to announce or declare publicly', and 战 (zhàn) means 'war' or 'battle'. Together, they form a formal, official verb meaning 'to declare war', typically used by a state or sovereign authority against another state. It implies a solemn, legal, and diplomatic act that precedes armed conflict and often follows international protocols.

This term appears in historical accounts, political news, diplomacy-related texts, and formal speeches. It is not used for personal disputes, metaphorical conflicts, or casual speech — saying 'I declare war on my alarm clock' would be humorous and inappropriate. While related to military action, 宣战 specifically refers to the *formal announcement*, not the fighting itself. It carries strong connotations of gravity, legitimacy, and consequence, distinguishing it from informal or emotional expressions of hostility.