Greenwich Longitude is a term that refers to the longitude line that passes through the Royal Observatory located in Greenwich, London. This line is used as a reference point for calculating longitude and is commonly referred to as the Prime Meridian. However, there are several other synonyms for Greenwich Longitude including the Greenwich Meridian, the Greenwich Prime Meridian, and the Zero Meridian. Alongside these synonyms, there are also additional terms such as the International Meridian, Universal Meridian, and World Meridian, all of which refer to the same line of longitude running through Greenwich. These terms are all used interchangeably in cartography, navigation, and timekeeping, all fields of the utmost precision where the most precise language and terminology is vital.