Ōdachi

An ōdachi (大太刀^?) (large/great sword) or nodachi (野太刀, field sword) was a type of traditionally made Japanese sword (日本刀, nihontō) used by the samurai class of feudal Japan. The Chinese equivalent and 'cousin' for this type of sword in terms of weight and length is the Miao dao, and the Western battlefield equivalent (though less similar) is the Spanish Espada Bastarda or Scottish Claymore.

The character for ō (大) means "big" or "great". The dachi here (太刀) is the same as tachi (太刀, lit. "great sword"), the older style of sword/mounts that predate the katana. The chi is also the same character as katana (刀) and the tō in nihontō (日本刀 "Japanese sword"), originally from the Chinese character for a blade, dāo.

To qualify as an ōdachi, the sword in question would have a blade length of around 3 shaku (35.79 inches or 90.91 cm); however, as with most terms in Japanese sword arts, there is no exact definition of the size of an ōdachi.

Practically speaking, the function/use of most ōdachi fall into the first two categories—as ceremonial objects and infantry swords. The possible functions of the ōdachi can be categorized as follows:

Ōdachi are difficult to produce because their length makes traditional heat treatment more complicated: The longer a blade is, the more difficult (or expensive) it is to heat the whole blade to a homogenous temperature, both for annealing and to reach the hardening temperature. The quenching process then needs a bigger quenching medium because uneven quenching might lead to warping the blade.

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