Dairy cheeses, especially hard, ripened varieties such as cheddar and Parmesan, usually contain a meat byproduct called rennet, an enzyme extracted from calf stomachs used to coagulate milk. Pig pepsin is another coagulating agent. Fresh, unripened dairy cheeses, such as cream cheese and goat cheese, usually contain vegetable rennet, a microbial enzyme produced from a mold culture. This is sometimes listed on labels as "cheese culture." Cheese spreads sometimes contain gelatin, another meat byproduct. Some dairy cheeses available in natural food stores are labeled rennetless or rennet-free. These are made with chymosin, a genetically altered bacteria that reproduces the "blueprint" of a cow rennin gene. Chymosin is usually listed on cheese labels as "enzymes."
Another label to look for is kosher. Kosher cheeses are rennetless because Jewish dietary law forbids the mixing of dairy and meat byproducts. Soy and nut cheeses, while free of meat byproducts, usually contain a milk protein called calcium caseinate, sodium caseinate or casein. Call the manufacturer to determine if a dairy cheese contains meat byproducts or if a nut or soy cheese contains milk byproducts.

This definition is in context to Vegetarian. See more contextual defintions for Cheese.