Swords typically have two edges, known as the cutting edge and the back edge. This characteristic design is primarily intended to enhance the sword's effectiveness as a cutting weapon. Here are a few reasons why swords have two edges:

1. Cutting Efficiency: Having two edges allows for a more efficient cutting action. The primary cutting edge is typically sharpened and used for delivering slashing or cutting attacks, while the back edge, also known as the false edge, can be used for secondary or follow-up strikes. This design enables the sword to inflict deeper and more devastating cuts on an opponent.
2. Versatility: The dual-edged design of a sword increases its versatility in combat. It provides the wielder with a broader range of attack and defense options. With both edges, the sword can be used for both cutting and thrusting techniques, allowing the wielder to adapt to different situations and engage various targets effectively.
3. Counterbalancing: The presence of a back edge helps to counterbalance the weight of the cutting edge, providing better overall balance to the sword. This balance facilitates ease of handling, agility, and control during combat, enhancing the wielder's ability to deliver precise strikes.
4. Historical Evolution: The use of two-edged swords has a long historical tradition. Throughout the evolution of sword designs in different cultures and time periods, the incorporation of two edges became a prevalent and effective approach to swordsmithing. The design proved its efficacy in battle and has been refined over centuries.

It's important to note that not all swords have two edges. Some historical swords, such as certain types of rapiers or thrusting swords, feature a single-edged or primarily single-edged design. The specific design of a sword is influenced by factors such as cultural traditions, historical context, intended purpose, and the evolution of weapon technologies over time.