In economics, additive utility is a cardinal utility function with the sigma additivity property.
Additivity (also called: linearity or modularity) means that "the whole is equal to the sum of its parts". I.e, the utility of a set of items is the sum of the utilities of each item separately. It says that for every bundle
An equivalent definition is: for all sets
An additive utility function is characteristic of independent goods. For example, an apple and a hat are considered independent: the utility a person receives from having an apple is the same whether or not he has a hat, and vice versa. A typical utility function for this case is given at the right.