～長
～ちょう · ～chou · JLPT N2 · noun
leader
👑 長 also means long: the one with the most years is the head, as in 社長, 校長
The old form of 長 showed an elder with long hair, so seniority came to mean authority. Put it after a group and you get that group's head: 社長 (company president), 校長 (school principal), 部長 (department head).