完毕 is a formal, written adjective meaning 'completed' or 'finished'. It combines 完 (wán), meaning 'complete' or 'entire', and 毕 (bì), meaning 'ended' or 'concluded' — together they reinforce the sense of full completion. Unlike colloquial terms like 完了 (wán le) or 结束 (jiéshù), 完毕 carries an official, procedural tone and is common in announcements, reports, work logs, and administrative contexts.

You’ll often see it after verbs in the structure [Verb] + 完毕 (e.g., 测试完毕, 'testing completed'), or used predicatively with 是 or 了 (e.g., 任务已经完毕, 'the task has been completed'). It’s rarely used in casual speech — native speakers typically choose simpler alternatives when chatting with friends or family. Its formality makes it especially frequent in workplaces, education, and official documentation.