The katana is a kind of weapon, unique among swords in that there is a blade on only one side. It is usually curved in order to increase cutting power. Katana are classified into 3 main groups according to their length: Katana (long sword, also called taitou or datou), wakizashi (short sword) and tantou (dagger). The sword has two main sections: the toushin (sword blade) and the exterior parts. The various exterior parts may be further classified as the saya (scabbard), tsuka (hilt or handgrip) and tsuba (the guard).