We have a basic idea of what a sandwich is: two slices of bread with some tasty stuff in between them, just as the Earl of Sandwich so ingeniously envisioned back in the 18th century. But get past those basics for form, and the specifics of function can make things … tricky. Is a hot dog a sandwich? What about a wrap? What about a gyro? Has an open-face “sandwich,” with its single slice of bread, been lying to us this whole time?