Several parts combine into one character.

際 is a phonetic-semantic compound: 阝 (the "mound / hill" radical, on the left) + 祭 (jì, "to sacrifice / festival" — providing the sound). The composite reads as "the edge / boundary at the foot of a hill" = the border between regions. The conceptual extension is striking: from spatial boundary → temporal boundary (the time-edge between events) → relational boundary (between people / nations). One character spans physical, temporal, and social meanings of "between." Mainland simplified to 际.

Korean reading "je." 國際 (gukje, international — top-frequency Korean political/economic term, used in compounds like gukje-sahoe "international community" and gukje-gwangye "international relations"), 實際 (silje, actual / real — used as adverb siljero "in reality"), 此際 (chaje, "at this juncture" — formal), 邊際 (byeonje, edge / border). Korean modern vocabulary depends on 국제 across diplomacy, business, and academia.

Mandarin jì, 4th tone (simplified 际). 国际 (guójì, international), 实际 (shíjì, actual / practical), 人际 (rénjì, "between people" = interpersonal — 人际关系 rénjì guānxi "interpersonal relationships"), 之际 (zhījì, "at the juncture of" — classical conjunction). Modern Chinese uses 国际 ubiquitously in news and policy.

Japanese on-reading サイ (sai) — 国際 (kokusai, international — Japan's 国際化 kokusaika "internationalization" was a defining 1980s concept), 実際 (jissai, actually / in reality — used as conversational adverb), 交際 (kōsai, social interaction / dating — 交際相手 kōsai aite "dating partner"), and the grammaticalized ~際 (sai, "at the time of / when"). Kun-reading きわ (kiwa) — 際 (kiwa, edge / verge), 窓際 (madogiwa, "window-edge" = window seat / by the window). The phrase 〜の際には (~ no sai ni wa, "at the time of / when ~") is a polite formal expression: ご来店の際には ("when you visit our store"), 緊急の際には ("in case of emergency").

Memory aid: hill (阝) plus festival (祭) — the edge / juncture where things meet = boundary in space, time, and relationships.