The word 内部 is formed by combining two characters, each contributing its core meaning to create a new, composite concept. The first character, 内 (nèi), means "inside" or "internal". It is placed alongside the second character, 部 (bù), which means "part", "section", or "division". When joined, they directly and logically combine to mean "the inside part" or "internal section", effectively forming a single term for "interior" or "within".