Just so that people are aware: 'sushi' is vinegar'd rice. That's what the name means in Japanese. 'Su' is vinegar made from rice-wine.
Raw fish (aka sashimi = 'cut meat') is often found on sushi but is by no means a requirement. Think of it like butter in a sandwich. It's usually there but a sandwich without butter is still a sandwich 
Nor is the dried seaweed (Nori) a requirement either but it is also often found on sushi. Nori allows for sushi to be eaten with the fingers.
 The Swiss singer Mani Matter has a good song about the dialectics of sandwiches.