This article is from the Vegetarianism FAQ, by firstname.lastname@example.org (Michael Traub) with numerous contributions by others.
Rennet is derived from the stomach linings of calves. Rennet is
used to make cheese. True VEGETARIAN cheeses do not have rennet in
them, but a substitute. These substitutes can be either from
vegetable sources, or may be created in a lab. Vegetable rennet is
usually called 'rennin' to distinguish it from the animal-derived
type. ** NOTE ABOUT SOY CHEESE: Some soy cheeses contain cassein
which is a milk-product. The only true VEGAN cheeses in the U.S.
are: SOYMAGE and VEGAN RELLA. In the U.K. there is also a vegan