SI
noun [ U ] science specialized uk/esˈaɪ/ us/esˈaɪ/
国际单位制（Système International 的缩写）
abbreviation for Système International: the international system of units used for scientific measurements, with standard base units such as the metre and the kilogram
The SI unit of electric current is the ampere. 电流的国际单位制单位是“安培”。