Marinara sauce can be spaghetti sauce, but not all spaghetti sauces are marinara sauces. Although the terms spaghetti sauce and marinara sauce are used interchangeably in the United States, there is a distinction between the two. Marinara sauce is prepared with specific ingredients.
Marinara sauce is made from tomatoes, tomato juice, oregano, garlic, basil and olive oil. Sometimes chili flakes or peppers are added as well. When other ingredients are added, however, it is no longer marinara sauce. Spaghetti sauces with ingredients such as sausage, peppers, olives or mushrooms are not marinara sauces. Rather, they are tomato-based sauces. It is also not uncommon for both spaghetti sauce and marinara sauce to be referred to as tomato sauce in the United States. In Italy, however, the name of the sauce typically changes based on the ingredients that added to it. Bolognese sauce, for instance, is usually made with ground meat. Many sauces in Italy are also of regional origins and evolved as the result of ingredients that were plentiful in those areas. Marinara sauce, for example, originated in Naples. Other regional sauces with similar ingredient line-ups to marinara sauce exist but have different names based on the region in which they originated.