境界
きょうかい · kyoukai · JLPT N2 · noun
boundary
🚧 境 (border) + 界 (world): the line where one world ends and another begins
境 means border or edge of land; 界 means realm or world. Together they name the boundary dividing two realms. Sound hook: 'kyou-kai' sounds like 'Kyoto' plus 'K-eye', so think Kyoto's city line.
界 — field 田 + scope 介
界 combines 田 (field) as the semantic component with 介 (jiè) as the phonetic. The original sense referred to boundaries between fields, then broadened to any border, limit, or realm — yielding modern meanings like 'world' (世界) and 'boundary' (边界).