A sausage consists of ground meat, animal fat, salt, and spices, and sometimes other ingredients such as herbs, usually packed in a casing. Sausage making is a very old food preservation technique.
Historically the casing has been the intestines of the animal, though it is now generally synthetic. Sausage may be fresh or preserved by curing or smoking.
There is no consensus on whether similar products that are not packed in casings - such as pâté, meatloaf, scrapple, and head cheese - should be considered sausages.