继任 means 'to succeed (to a position)' — specifically, to formally take over a role, office, or responsibility previously held by someone else. The character 继 (jì) means 'to continue' or 'to follow', and 任 (rèn) means 'to assume (a duty or post)' or 'to appoint'. Together, they form a compound verb emphasizing the orderly, legitimate transition of authority or function — commonly used for leadership roles such as president, CEO, professor, or department head.

This word is formal and written-register dominant; it rarely appears in casual speech. It often occurs in news reports, official announcements, academic contexts, or organizational documents. While it can be used transitively (e.g., 继任校长), it frequently appears with prepositions like '为' (as in 继任为…), '为…所继任', or in passive constructions. It implies continuity and legitimacy — not just replacement, but succession in line with rules or tradition.