the prime meridian

剑桥词典

the imaginary line from the North Pole to the South Pole that passes through Greenwich in England and marks 0° longitude , from which all other longitudes are measured
本初子午线（从北机到南极的一根假想线，它穿过英格兰的格林尼治，标示为经线0°，其他经线以此为测定标准） 返回 the prime meridian