None of these definitions are universally accepted.
A taco is a sandwich A hot dog is a sandwich A burger is a sandwich
There is such a thing as an open-faced sandwich, which has one slice of bread.
A taco is a sandwich A hot dog is a sandwich A burger is a sandwich
There is such a thing as an open-faced sandwich, which has one slice of bread.
Open-face sandwiches often have multiple pieces of bread, go by many names, and are similar to toasts and tostadas, which are neither sandwiches nor tacos.