Arcus posterior atlantis is a Latin term used in anatomy to describe a bony ridge on the back of the first cervical vertebra, also known as the atlas. Though not frequently encountered, this anatomical feature has some synonymous terms that are used interchangeably. These include "posterior atlantal arch", "atlas posterior arch", and "atlantal posterior bridge". These synonyms help medical professionals and anatomists to better communicate and understand this specific structure, facilitating accurate descriptions and diagnoses. Whether it is referred to as arcus posterior atlantis, posterior atlantal arch, atlas posterior arch, or atlantal posterior bridge, the meaning remains the same, providing a clear reference to this specific bony ridge on the first cervical vertebra.