Which of the following describes the term "roll"?

The term "roll" specifically refers to the gradual side-to-side motion of a ship as it moves through water. This motion occurs due to the ship's stability and buoyancy, leading to the lateral tilt or inclination of the vessel around its longitudinal axis.

When a vessel encounters waves, especially in rough sea conditions, it can roll from side to side as it responds to the forces acting on it. This is a normal part of a ship's movement and is an important factor for marine navigation as excessive rolling can affect the ship's stability, cargo security, and overall handling.

Other options describe different aspects of a ship's movement: a vertical motion refers to pitch, a steady forward movement is related to the ship's progress or speed, and a sudden change in direction pertains to yaw. Understanding these terms helps in comprehending how various forces affect a vessel while it is operating at sea.