成人
せいじん · seijin · JLPT N3 · noun
adult
🧑💼 成人 = become + person: someone who has become a full person
成 (sei) means to become or complete, and 人 (jin) means person. An adult is a person who is fully grown. Japan celebrates 成人の日 (Coming of Age Day) for people who turn adult.
成 — 戊 (halberd/weapon) + 丁 (nail/man)
Originally a pictograph of a halberd or axe-like weapon, suggesting the act of completing a task by force. Over time it shifted from 'to subdue' to the broader meaning 'to accomplish' or 'to become'. The 丁 element inside also hints at the chéng sound.
人 — pictograph of a standing person
人 is a pictograph showing a person viewed from the side, with two strokes representing the legs and torso of a standing human. In oracle bone script it clearly depicted a figure leaning slightly forward. The meaning has remained 'person' or 'human' throughout its history.