What is the term used for the angular difference between magnetic north and true north?

The term for the angular difference between magnetic north and true north is known as variation, often referred to as magnetic declination. Variation is the term that describes how much the magnetic north differs from true north at a particular location on the Earth's surface. This difference can vary based on geographic location and can change over time due to shifts in the Earth's magnetic field.

Understanding variation is crucial for navigation, as it ensures that navigators can accurately determine their heading and make adjustments to account for this difference when using a compass. By recognizing the value of variation in navigational practices, individuals can improve their accuracy when plotting courses or heading towards specific destinations.