Ammunition is the supply of bullets, shells, and other projectiles that guns and other weapons fire. A soldier carries ammunition for their rifle, a hunter brings ammunition for their shotgun, and a police officer's ammunition might be stored in magazines attached to their belt. Without ammunition, a gun can't fire.

Different weapons need different types of ammunition: a small pistol uses small bullets, while a cannon fires large explosive shells. Video games often show characters collecting ammunition to keep their weapons working, which reflects the real challenge soldiers face: running out of ammunition in the middle of a battle.

People also use ammunition metaphorically to mean any resource that helps you in a conflict or argument. If you discover that your sister broke Mom's favorite mug, that information becomes ammunition you might use in your next disagreement. When a debater finds a weak point in their opponent's argument, they've gained ammunition for their rebuttal. In this sense, ammunition means anything that strengthens your position or helps you make your case.