What is the distinction between magnetic variation and magnetic deviation?

1. Variation is the angle between True North and Magnetic North; deviation is the compass error caused by local magnetic fields within the aircraft.
2. Deviation is the angle between True North and Magnetic North; variation is the compass error caused by local magnetic fields within the aircraft.
3. Variation changes with the aircraft's heading; deviation is constant worldwide.
4. Deviation is corrected by aligning the gyro; variation is corrected by adjusting the altimeter setting.