The word "局长" is formed by combining two individual characters, each contributing its core meaning to create a new, specific concept. The first character, "局" (jú), originally referred to a part or segment but evolved to mean an office, bureau, or administrative department. The second character, "长" (zhǎng), carries the fundamental meaning of "chief", "head", or "leader". By placing "长" after "局", the compound directly and logically signifies "the head of the bureau", where the first element defines the domain or institution, and the second defines the leadership role within it.