The other part of the set is the Wakizashi, about half the lenght of a normal katana, used by samurais not in combat, but in the ceremony of seppuku, being also called the guardian of honor.
We also have the Tachi, which is usually longer and more arcuated, but is considered a tachi a sword that can be attached to the obi with the edge turned down, in opposition to the katana where to edge is up, used mostly by the cavalry.
We must also remember the kodachi, which is a small tachi, not long enough to be considered a katana, but still longer than a tanto(japanese knife), it could be used by non samurais since it was smaller than the limit imposed by law for self.defense purpose.