What is the term for the fattened liver of a special type of duck or goose?

The term for the fattened liver of a special type of duck or goose is foie gras. This delicacy is created through a process called "gavage," where the birds are fed a high-starch diet to enlarge their livers significantly. Foie gras is prized in culinary circles for its rich, buttery flavor and smooth texture, making it a luxurious ingredient in French cuisine.

In contrast, pâté refers to a mixture of ground meat and fat that can include liver but is not exclusively made from the fattened liver of specific types of ducks or geese. A terrine is a dish made from a mixture of ingredients set in a mold, often containing various meats, vegetables, and sometimes pâté, but not specifically about the preparation of duck or goose liver. Rillettes, on the other hand, is a spread made from pork or other meats that are cooked slowly in fat until tender and then shredded, distinguished from the specialized nature of foie gras. Thus, foie gras stands out as the specific term for the fattened liver from these birds.