The expression double-edged sword implies that an action or decision which appears to help can also harm the sword holder. Metaphorically speaking, a sword with two edges would solve one problem, but could potentially cause even more problems on the back swing. Some sources also suggest the expression cuts both ways also covers the same territory, meaning favorable consequences on one side can lead to unfavorable consequences when the double-edged sword swings back.

A single-edged sword is generally used for slashing and cutting from a mounted or superior position. A samurai sword or katana would be an example of a single-edge sword. A double-edged sword, like a rapier, would be used in battle to engage enemies approaching from both sides of the fighter. A double-edged sword would be equally as deadly swung to the left or right, and could possibly injure the swordsman himself if not handled properly.

In a business setting, an employer might describe a pay raise as a double-edged sword. While an employee may benefit from the increased pay, the money needed to finance the raise may have to come from another department's budget. Others may see a government military operation as a double-edged sword, since the effect of a quick victory may be the destabilization of the entire region. A number of situations in which the same action that heals can also harm could be described as double-edged swords.

There are some etymologists who question the accuracy and appropriateness of the metaphorical double-edged sword. In real life, a sword with two edges does twice as much damage, with only a minimal risk to the wielder. There is no tangible harm/heal relationship, but the expression suggests one. The concept of an action or decision cutting both ways does seem plausible, but the wielder of a double-edged sword is generally protected from the blade. Critics suggest a different weapon such as a double-tipped spear implies more of a mutual threat than an actual double-edged sword.

Regardless of its historical or military accuracy, the expression does succeed in describing a potentially dangerous situation with unforeseen ramifications for the person wielding the double-edged sword. Whenever such a situation arises, it pays to examine both sides of the issue to make sure the sword's return stroke does not make matters worse.