首都 (shǒu dū) literally means 'first city' — 首 (shǒu) means 'first', 'head', or 'chief', and 都 (dū) means 'capital' or 'metropolis'. Together, they form a formal, standard term for the capital city of a country — the political, administrative, and often cultural center. Unlike more colloquial terms like 市 (shì, 'city') or 省会 (shěnghuì, 'provincial capital'), 首都 specifically refers to the national capital and carries official weight.

This word is commonly used in geography, news reports, textbooks, and formal writing. It appears in compound phrases such as 首都机场 (shǒu dū jīchǎng, 'capital airport') or 首都圈 (shǒu dū quān, 'capital region'). While it can refer to capitals of other sovereign states (e.g., 巴黎是法国的首都), it’s most frequently used when discussing China’s capital, Beijing — as in 北京是中国的首都.