Doritos is a brand of corn chip: thin, crunchy triangles made from maize, usually covered in a strong flavour (cheese is the famous one). It is a trademark, so you write it with a capital D, like a name. In everyday English, though, people often say Doritos the way they say Kleenex — they mean that kind of bagged chip, even when the packet is another brand. Teenagers, parties, and snack adverts use it constantly; it is informal food talk, not a textbook word. The chips started in the United States and then travelled the world. You eat them from the bag, or with a dip. There is no polite “Dorito” in careful writing for the idea “any corn chip”; if you want the general food, say corn chips or tortilla chips. Though actually, once the brand is in the room, almost nobody bothers — they just ask for the Doritos.