What is the definition of 'ground speed' in aviation terms?

Ground speed refers to the speed of an aircraft in relation to the surface of the Earth, specifically the ground beneath it. It is an important measure for pilots as it reflects how quickly the aircraft is moving in relation to a fixed point on the ground. This measurement takes into account the effects of wind; for instance, a headwind will reduce ground speed compared to the aircraft's true airspeed, while a tailwind will increase it.

Understanding ground speed is crucial for navigation, flight planning, and estimating arrival times, as it directly influences the duration of the flight. The concept emphasizes the distinction between an aircraft's motion through air (airspeed) and its actual motion over the ground, making it a key parameter in aviation.