‘建交’ is a verb meaning ‘to establish diplomatic relations’ between two countries. It combines 建 (jiàn), meaning ‘to build’ or ‘to establish’, and 交 (jiāo), short for 外交 (wàijiāo, ‘diplomacy’) or 交往 (jiāowǎng, ‘exchange/relations’). Together, they literally mean ‘to build relations’, specifically formal state-to-state diplomatic ties. This term is used almost exclusively in political and international contexts — for example, when two nations open embassies, sign agreements, or publicly announce mutual recognition.

The word is formal and official; it rarely appears in casual speech. It’s often used in news reports, government statements, and history textbooks. Note that ‘建交’ refers only to the *act of establishing* relations — not ongoing diplomacy (which uses terms like ‘维持外交关系’ or ‘发展双边关系’). It’s typically followed by ‘与…’ (with…) or ‘同…’ (with…), indicating the other country involved.