In the context of traditional Japanese swords, such as the katana, there are three primary classifications based on length:

1. Daito: Daito refers to a long sword. It is the standard-sized katana, typically measuring around 60 to 80 centimeters (24 to 31 inches) in blade length. The daito is the most commonly recognized and widely used katana. It served as the primary weapon of the samurai and was used for various combat techniques.
2. Shoto: Shoto refers to a short sword or a companion sword. It is often used as a secondary weapon to accompany the daito. The shoto, or wakizashi, typically has a blade length of around 30 to 60 centimeters (12 to 24 inches). It was traditionally worn alongside the daito as part of the samurai's daisho, symbolizing their social status and readiness for different combat situations.
3. Tanto: Tanto refers to a dagger or a short knife. It is the smallest of the three katana types, with a blade length typically less than 30 centimeters (12 inches). The tanto was used primarily as a stabbing weapon or for close-quarters combat. It was often carried as a self-defense weapon or as a utility knife by samurai, as well as by commoners for various purposes.

These three types of katana—daito, shoto, and tanto—represent a progression of blade lengths, from long to short. Each type had specific purposes and applications, reflecting the needs and preferences of the samurai in different combat situations.

It's worth noting that there may be variations within these classifications, and other specialized types of katana may exist for specific purposes, such as the uchigatana used by samurai cavalry or the odachi, an extremely long sword. However, the daito, shoto, and tanto are the primary and most recognized categories within the traditional classification of katana based on length.