What Defines a Burger?

It's National Burger Month, and we find ourselves asking: what makes a burger a burger? Is it the bun? Or the patty? Must it be made with ground beef, or can it be any kind of ground meat or protein? It all depends on how you define "burger," which is truly an existential question for our modern foodie times. Before we get bogged down in a highbrow burger debate, let's do this the easy way: click through the gallery of burgers and cast your vote on which should be considered a true burger and which ones are undeserving of the title.