The Japanese sword is probably the most perfect cold weapon ever produced by mankind. With few exceptions, it is curved and single-edged. Japanese sword was perfected during the Heian Period (794-1185) and continued to be the indispensable weapon of samurai, the “warrior class” of feudal Japan - and symbol of their spirit - until the end of the nineteenth century.
By convention, Japanese swords are divided into four types accordingly to their length, but nomenclature has changed over the centuries and one should also remember that “katana” is the general term for Japanese “sword”.
Tachi was the long Japanese swords (over 60 cm, but often reaching 80 cm) used with one hand by armored samurai on horseback from the Heian period.
Katana swords, used from the Muromachi period, where worn through the sash, edge uppermost. Again, these are long Japanese swords, over 60 cm. By law, samurai only could wear a katana.
Wakizashi was the shorter of the two swords, worn at all times by the samurai, whereas the katana were usually carried out of doors in a pair with the wakizashi. Lenght is between 30 cm and 60 cm.
Tantō, single or double-edged, has a length between 15 and 30 cm. The tantō was designed primarily as a stabbing weapon, but the edge can be used for slashing as well.