What is the difference between a gun and a cannon?

Answer 1

All cannons are guns, but not all guns are a cannon. A cannon is typically a large diameter firearm, NOT fired from the shoulder or hand, and fires in a direct fire mode (barrel angle less than 45 degrees to the ground. For instance, the .50 caliber machine gun is a gun, but the 20mm cannon has a larger bore diameter, and is not fired from the shoulder. During the first World War, there was a 20mm anti-tank rifle. Despite the size of the bore, it was fired from the shoulder (OUCH!) and is not a cannon. With some artillery peices, those that can only fire in a direct fire mode, they may be designated as guns, to distinguish them from howitzers, which CAN shoot high angle fire.