逐一 means 'one by one' or 'individually', emphasizing careful, sequential attention to each item in a group. The character 逐 (zhú) conveys the idea of 'pursuing' or 'following closely', while 一 (yī) means 'one'; together, they form an adverbial phrase indicating methodical, item-by-item handling. It often implies thoroughness and intentionality — not just counting, but examining, checking, or dealing with each element separately.

This word is commonly used in formal, instructional, or procedural contexts: verifying documents, inspecting items, completing tasks on a checklist, or teaching step-by-step processes. It frequently appears after verbs like 检查 (jiǎnchá, 'to check'), 核对 (hèduì, 'to verify'), or 完成 (wánchéng, 'to complete'), and is rarely used in casual speech or emotional expressions. While it can modify verbs directly, it does not function as a noun or adjective — it always describes *how* an action is carried out.