边境
biān jìng · HSK 5
border
🛂 边 = side/edge + 境 = territory/realm = edge of the realm
边 means side or edge (as in 边缘 edge). 境 means territory or boundary-state (as in 国境 national border, 环境 environment). Together: the edge-territory where one realm ends and another begins.
边 — 辶 (walk) + 臱 (phonetic)
边 is the simplified form of 邊. It combines the walking radical 辶 with the phonetic component 臱, suggesting a place reached by walking — the edge or border of a territory. The meaning extended from 'frontier' to 'side' or 'edge' in general.