Many shapes of Japanese knives can be used to cut vegetables, but these 2 shapes are specifically designed for this use.
The nakiri knife is the ultimate vegetable knife. It features a straight, symmetrical edge ideal for precision and uniform vegetable cuts. Unlike the all purpose knives, the nakiri has a straight edge for cutting in an up-and-down motion. Because this knife has a thin blade it can be easily chipped if you use the knife outside its intended purpose.
The usuba knife is like the nakiri with the flat, straight edge, however the main 2 differences is that the usuba has a single beveled edge and has a heavier spine. The usuba was designed to be used with traditional Japanese techniques that take skill and practice to use. The 'western' version of the usuba is the nakiri.