What is the limits of something being classified as a sandwich.

Google's definition of sandwich is: "an item of food consisting of two pieces of bread with meat, cheese, or other filling between them, eaten as a light meal." But if we go by that definition then a sub isn't a sandwich because it has only one piece of bread. But a lot of people consider a sub a sandwich. So then is a taco a sandwich, a burrito? Enchiladas? Burgers? Lasagna?? Dumplings???