system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are dominantly slashing weapons curved? Why do some curve backwards, which some curve forwards?
gpt
Few curve forwards and those ones are usually more for special purposes. Medieval polearms with backward hooks such as bills were intended to allow you to grab onto riders and de-horse calvary, or pull shields away from their bearers, for example. 

For the ones that curve backward and away from the point of impact, it's so you can cut better and reduces the chances that your weapon will get stuck. When the edge of your swinging weapon is straight and you connect, it's harder to slice the weapon out and do further damage than if it's a curved edge like a cutlass. Weapons like the longsword were largely "hit, then pull backward from the direction you just swung to hit again". With the cutlass or katana, you "hit and continue slicing to pull your weapon free" to do more damage, cut tendons and increase bleeding, you don't just pull it back.