‘前夕’ literally combines ‘前’ (qián, meaning 'before' or 'prior to') and ‘夕’ (xī, meaning 'evening' or 'dusk'). Together, it denotes the evening or day immediately before a significant event—functioning as the Chinese equivalent of 'eve', such as 'the eve of Christmas' or 'the eve of graduation'. Unlike the English word 'eve', which historically refers specifically to the evening before, 前夕 in modern usage often extends to the entire day (or even the final 24–48 hours) preceding an important occasion. It carries a formal, slightly literary tone and is commonly used in news reports, speeches, official announcements, and written narratives.

This term is almost exclusively reserved for notable, culturally or personally meaningful events—such as holidays (Spring Festival, National Day), life milestones (graduation, wedding, retirement), or historic moments (Olympics, major policy launches). It is not used for routine or trivial occurrences. Its compound structure makes it a fixed noun; it cannot be modified with adjectives like ‘very’ or split apart, and it does not take aspect markers like 了 or 过.