The main difference between an odachi and a katana lies in their size, length, and intended use.

Odachi:

• The odachi, also known as nodachi, is a type of Japanese sword that is considerably longer than a standard katana.
• Odachis typically have a blade length of around 3 to 4 feet (approximately 91 to 122 cm) or even longer, although precise measurements can vary.
• The extended length of the odachi makes it difficult to handle with one hand, and it is typically wielded with both hands.
• Odachis were historically used by samurai warriors on foot or sometimes by soldiers fighting from horseback.
• Due to its size and weight, the odachi was primarily employed in open-field battles or in specific combat scenarios that allowed for its effective use.
• The odachi is characterized by its long blade, which provided reach and cutting power, making it suitable for engaging multiple opponents or disrupting enemy formations.

Katana:

• The katana is a traditional Japanese sword with a curved, single-edged blade.
• Katanas typically have a blade length of around 2 to 2.5 feet (approximately 61 to 76 cm), although there can be variations.
• The katana is designed to be wielded with two hands but can also be used effectively with one hand when necessary.
• Katanas were the primary weapon of the samurai class during feudal Japan and were versatile blades used for various combat situations.
• The curved blade of the katana allows for efficient cutting and slicing motions, while its balanced design enables quick and agile movements.
• Katanas were worn with the cutting edge facing upward and were often paired with a smaller companion sword, such as a wakizashi, as part of the samurai's daisho.

In summary, the key differences between an odachi and a katana are their size, length, and intended use. Odachis are longer, heavier swords designed for two-handed use, while katanas are more compact and versatile weapons that can be used with one or two hands.