The Tachi is a long, traditional Japanese sword that was developed before the creation of the katana. They are usually 70-80 cm in length, but vary greatly.
Large tachi were termed oOdachi, while smaller ones were called Kodachi. The tachi is the predecessor to the Uchigatana, and the two often differentiated from each other only by how they were worn, the fittings for the blades, and the location of the signature (mei).