What is the definition of deviation in navigation terms?

Deviation in navigation terms refers specifically to the error in compass readings caused by magnetic interference within the aircraft. This interference can arise from onboard magnetic fields, such as those generated by the aircraft's electrical equipment or metal structures. It leads to inaccuracies in the compass heading, which must be accounted for by pilots when navigating. Correcting for deviation is crucial for ensuring that the aircraft is following the intended course accurately, as relying solely on the compass without adjusting for deviation can lead to navigation errors.

The other options relate to different aspects of navigation. The distance traveled versus the intended flight path pertains to the concept of ground track, while the difference between true airspeed and ground speed reflects the influence of wind on the aircraft's actual speed over the ground. Adjustments made for wind drift are essential for flight planning and accuracy but do not constitute deviation in compass navigation.