Define 'yaw' in the context of aircraft motion.

Yaw refers to the rotational movement of an aircraft around its vertical axis. This motion is essential for changing the aircraft's direction horizontally without altering its altitude. When an aircraft yaws, it moves its nose to the left or right while its wings remain level, allowing for coordinated turns and directional control during flight.

In practical terms, yaw is controlled primarily by the aircraft's rudder, which is located on the vertical stabilizer. When the pilot applies rudder input, the aircraft rotates about its vertical axis, facilitating smoother turns and maintaining directional stability, which is crucial for maneuvering effectively and responding to wind conditions or other influences during flight. Understanding this concept is fundamental for pilots, as it affects how they navigate their aircraft in various flight conditions.