The word 外部 is a compound noun formed by combining two independent characters: 外 (wài), meaning "outside" or "external", and 部 (bù), meaning "part", "section", or "department". It follows a common grammatical structure in Chinese known as a modifier-head or attributive construction, where the first character 外 modifies and specifies the second character 部. Literally, it means "the outside part", and by semantic extension, it refers to the exterior, the outside, or an external entity (such as an external department) in contrast to an internal one.