Yaw
Yaw is the rotational motion of a ship about its vertical axis — the swinging of the bow to port or starboard, side to side, off the intended heading. It is one of the vessel's six degrees of freedom of motion, and the one most directly related to steering and course-keeping.
A ship continuously yaws a little around its heading, corrected by the rudder (and the autopilot); excessive or uncontrolled yaw — for example in a following sea (broaching) or through steering difficulty — is a handling and safety concern. Yaw is distinct from the other angular motions roll (about the fore-and-aft axis) and pitch (about the transverse axis), and the linear motions surge, sway and heave. Understanding yaw is basic to ship handling, course-keeping, and the dynamics of steering, and the term is also used across aircraft and vehicle dynamics. It is a fundamental element of how a vessel moves and is controlled.
Yaw is the ship swinging off its heading — the motion the helm and autopilot are constantly fighting to keep a straight course. Uncontrolled, it becomes a real safety issue (broaching in a following sea). Understanding yaw, alongside roll and pitch, is basic to how a vessel steers and behaves at sea.
What is yaw on a ship?
Rotation about the vertical axis — the bow swinging left or right off the intended heading, corrected by the rudder and autopilot.
How is yaw different from roll and pitch?
Yaw is rotation about the vertical axis; roll is about the fore-and-aft axis (side to side tilt); pitch is about the transverse axis (bow up and down).