What is the term used for stairways on a vessel?

The term used for stairways on a vessel is "ladders." In nautical terminology, ladders are specifically designed for the unique conditions found on ships and boats. They offer a safe means of moving between different levels and are often constructed to be steep and lightweight to maximize space and safety on board. Unlike standard stairs found in buildings—which are generally wider and have more gradual inclines—ladders are built to accommodate the confined space and structural requirements of a vessel.

This terminology underscores the importance of differentiating between the various structures used for navigation in a maritime environment. Other choices like stairs, ramps, and steps might refer to similar concepts but lack the precise application in nautical contexts that the term "ladders" has.