The word "船长" is formed by directly combining two conceptual ideas: "船" (chuán), meaning "ship" or "boat", with "长" (zhǎng), which carries the core idea of "chief", "head", or "person in authority". It is a straightforward compound where the second element defines the role of the first, resulting in the unified concept of "the person who is the head/authority of the ship", i.e., a captain or shipmaster.