What term refers to the variance between magnetic north and true north?

The term that refers to the variance between magnetic north and true north is called variation, also known as magnetic declination. This concept is crucial for navigation as it accounts for the difference in degrees between the geographic north pole (true north) and the magnetic north pole, which is where a compass points.

Understanding variation is essential for navigators because, depending on the location, the angle between these two norths can significantly affect navigation. If a navigator does not compensate for this difference, their course may lead them off track.

In contrast to variation, deviation refers to the error introduced by the ship's own magnetic field affecting the compass reading, while direction is a broader term that refers to the orientation of something. Angle is also a general term and does not specifically denote the contrast between true and magnetic north. Thus, variation specifically addresses the navigation concern needed for accurate course plotting.