A semi-automatic, or self-loading firearm is a weapon which performs all steps necessary to prepare the weapon to fire again after firing—assuming cartridges remain in the weapon's feed device or magazine. Typically, this includes extracting and ejecting the spent cartridge case from the weapon's firing chamber, re-cocking the firing mechanism, and loading a new cartridge into the firing chamber. Although automatic weapons and selective fire firearms do the same tasks, semi-automatic firearms do not automatically fire an additional round until the trigger is released and re-pressed by the person firing the weapon.
While all basic firearm actions require the action to be cycled manually before the first shot, semi-automatic as well as automatic and selective fire actions are differentiated from other forms such as single-action or double-action revolvers, pump-action, bolt-action, or lever-action firearms by eliminating the need to manually cycle the weapon after each shot. For example, to fire ten rounds from a semi-automatic firearm or a selective fire weapon set to fire semi-automatically, the action would initially be cycled to load the first round and the trigger would need to be pulled ten times (once for each round fired). For the other forms, the weapon's mechanism would require cycling manually prior to firing the next round. An automatic or a selective fire weapon set to fire automatically would be able to fire continuously as long as the trigger is held until the magazine or feed device runs out of ammunition.