‘国界’ (guó jiè) literally combines ‘国’ (guó), meaning ‘country’ or ‘nation’, and ‘界’ (jiè), meaning ‘boundary’ or ‘limit’. Together, they form the precise term for the officially recognized line that separates one sovereign state from another — in other words, a national border. Unlike informal terms like ‘边界’ (biān jiè), which can refer to any boundary (including regional or property lines), ‘国界’ specifically denotes the legal, internationally acknowledged frontier between countries.

This word appears frequently in geography, politics, news reporting, and travel contexts. It implies formal recognition — often established by treaties, historical agreements, or international law — and carries legal and diplomatic weight. You’ll encounter it when discussing immigration, territorial disputes, cross-border trade, or maps showing sovereign territories. It is neutral in register and appropriate for both written and formal spoken Chinese.