a.k.a. the Side Sword, is an early type of rapier from the 15th-17th century. It was used by infantry against both armored opponents and unarmored. It was also used as a dueling weapon in the 16th and 17th century.
They can be anywhere from 36" to 42" (though I personally wouldn't want a single handed sword any longer then 36") and weigh 2 to 3 1/2 lbs.
In the early seventeenth century rapiers and side swords reached their height of fashion. It was also fashionable to ware as long of a sword as you could. Some even reached the length of 48". Of course a lot of noblemen were getting killed because their swords were too long and clumsy. That's probably why Queen Elizabeth limited the length of the blades in the 16th century.
Though it seems smart to have a long blade, if the blade is too long the weight of the steel makes it slow and clunky. Even if the sword was lighter you have to take into account the angles both of attack and defence. You need to be able to parry an attack to your legs without your sword getting stuck in the ground. And when your blade is a lot longer then your opponent then it is easy for them to parry your attack and clime in closer. Once they are inside the reach of your sword there's really isn't anything you can do.
Like the rapiers, side swords are good for both the thrust and the cut, though primarily the thrust. As a lighter weight weapon it would be a good choice for smaller or lighter character.