By SAM SIFTON

Here is a celebration of the sandwich’s diversity in the United States, an attempt to bring order to the wild multiplicity of its forms.

But first: What is a sandwich? The United States Department of Agriculture declares: “Product must contain at least 35 percent cooked meat and no more than 50 percent bread.” But a sandwich does not require meat! Merriam-Webster is slightly more helpful: “two or more slices of bread or a split roll having a filling in between.”

For the purposes of this field guide, we have laid down parameters. A hamburger is a marvelous sandwich, but it is one deserving of its own guide. The same holds for hot dogs, and for tacos and burritos, which in 2006, in the case known as Panera v. Qdoba, a Massachusetts judge declared were not sandwiches at all. Open-faced sandwiches are not sandwiches. Gyros and shawarmas are not sandwiches. The bread that encases them is neither split nor hinged, but wrapped.

There are five main families of sandwich in The New York Times Field Guide.

There are sandwiches made on Kaiser or “hard” rolls.

There are sandwiches made on soft buns.



There are sandwiches made on long hero or sub rolls.



There are sandwiches made on sliced bread.

And there are what we call “singulars,” which are those creations on bread that falls outside these other groups but are still vital to the sandwich landscape, like the muffuletta.

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