The term "normal earth-fixed axis system" refers to a coordinate system centered on the Earth's axis, which is fixed in space. However, there are several synonyms that can be used to describe this system. Some common alternatives include the "geocentric coordinate system," "Earth-centered coordinate system," or the "terrestrial reference frame." These terms all refer to the same concept of a coordinate system that is based on the Earth's position in space. The use of these different terms reflects the diversity of scientific disciplines that rely on this type of coordinate system, from astronomy to geodesy to satellite navigation.