‘首次’ literally combines ‘首’ (shǒu), meaning ‘first’ or ‘head’, and ‘次’ (cì), meaning ‘time’ or ‘occasion’. Together, they form an adverbial phrase meaning ‘for the first time’, emphasizing that something is happening or has happened for the very first instance in a sequence or lifetime. It is commonly used before verbs to modify the action — for example, ‘首次访问’ (to visit for the first time) or ‘首次发现’ (to discover for the first time).

This term is neutral in register and appears frequently in formal writing, news reports, academic contexts, and everyday speech when highlighting novelty or inaugural occurrence. Unlike the more colloquial ‘第一次’, ‘首次’ carries a slightly more formal or official tone and often appears in compound nouns (e.g., 首次亮相 — ‘first appearance’) or as a standalone adverbial modifier. It cannot function as a noun on its own — you wouldn’t say ‘这是我的首次’ without specifying what kind of event.