The word 外界 is formed by combining the character 外 (wài), meaning "outside" or "external", with the character 界 (jiè), meaning "boundary", "limit", or "realm". Conceptually, it is a direct and literal spatial synthesis: 外 establishes the notion of externality, and 界 defines it as a distinct sphere or domain, together creating the composite meaning of "the external world" or "the realm that exists beyond a specific boundary".