No, the ōdachi and katana are not the same type of sword. While they both originated in Japan and share some similarities, they have distinct characteristics that differentiate them from each other.

Ōdachi:

The ōdachi, also known as nodachi, is a long Japanese sword characterized by its exceptionally long blade. It typically has a blade length of around 90 centimeters (35 inches) or longer. The ōdachi was primarily used by foot soldiers and warrior monks during specific historical periods. It was employed in open-field battles and was particularly effective against cavalry due to its extended reach and cutting power.

Katana:

The katana is a more well-known and iconic Japanese sword. It has a curved, single-edged blade with a typical length ranging from around 60 to 75 centimeters (24 to 30 inches). The katana was the primary weapon of the samurai class and was used for a wide range of combat techniques. It was designed for versatile use, combining cutting power, maneuverability, and the ability to be worn with the cutting edge facing down.

While both the ōdachi and katana are traditional Japanese swords, the main distinction lies in their size and intended use. The ōdachi is a much larger weapon designed for specific combat situations, while the katana is a more versatile and commonly used sword by samurai warriors.

It's worth noting that terminology and definitions can vary between different historical periods and regions, and there can be overlap or variations in usage. The exact definitions and distinctions of ōdachi and katana can depend on specific historical contexts, regions, or sources.