The katana and odachi are both traditional Japanese swords with distinct characteristics that set them apart. Here are the key differences between a katana and an odachi:

1. Blade Length: The most notable difference between a katana and an odachi is the blade length. A katana typically has a blade length of around 60 to 75 centimeters (24 to 30 inches), while an odachi has an exceptionally long blade ranging from around 90 centimeters (35 inches) to over 120 centimeters (47 inches). The odachi's longer blade gives it greater reach and striking power compared to the katana.
2. Practicality and Usage: The katana was a practical and versatile weapon primarily used by samurai warriors. It was suitable for various combat situations and techniques, both on foot and horseback. In contrast, the odachi was primarily a battlefield weapon used by foot soldiers. Due to its size, it was less practical for use in confined spaces or on horseback. The odachi's length and weight made it more effective for sweeping strikes against multiple opponents or as an anti-cavalry weapon.
3. Handling and Technique: The katana is designed for one-handed use, allowing for quick and agile movements. Its balance and curvature make it effective for drawing cuts, thrusts, and precise strikes. On the other hand, the odachi is a two-handed sword that requires both hands to wield effectively. Its longer length and size necessitate different handling techniques and stances to maximize its power and reach.
4. Cultural Significance: The katana holds immense cultural significance in Japan and is associated with the samurai class and their code of conduct, Bushido. It represents discipline, honor, and the spirit of the samurai. The odachi, while also symbolizing the warrior class, is less commonly known and has a more specialized usage within historical contexts.
5. Evolution and Historical Periods: The katana has a longer history and wider usage throughout various historical periods in Japan, including the feudal eras. The odachi, on the other hand, was more prominent during specific periods and had a more specialized role as a battlefield weapon.

It's important to note that terminology and definitions surrounding swords can vary based on historical periods, regions, and individual sources. The distinctions between a katana and an odachi can sometimes blur, and there may be variations or overlap in their characteristics, usage, and terminology.