公里(gōng lǐ) - kilometre in Mandarin

公里 (gōng lǐ) is the kilometre, and it is the unit you will meet on every Chinese road sign, speedometer and running app. It slots straight after a number with no measure word in between: 五公里, 三百多公里.

The 公 in front is the same prefix that makes 公斤 (kilogram) and 公尺 (metre). It marks a unit as belonging to the international metric system rather than to the older Chinese one, which is why the pair 里 and 公里 sit side by side in the language.

The trap is that 里 on its own is not short for 公里. It is the old Chinese li, roughly half a kilometre, and it still turns up in set phrases such as 万里长城. Say the whole word. The other thing to unlearn is the plural: 公里 never changes shape, so twenty kilometres is 二十公里, not 二十公里们 or anything like it.