Marginal rate of substitution (MRS)

1) The extension of the rate on the Indifference curve at which a consumer would give up using one product/ service and switch to another one. For example, the more frequent the consumption of a product with a certain brands name is, the more likely it becomes for the consumer to start using the same product with a new brand soon instead, i.e. in this case the MRS decreases. This example illustrates the principle that the more a good is used the less is satisfaction of each additional unit.
2) The number of units of one product (i.e. hamburgers) that a consumer is ready to give up in order to obtain 1 extra unit of another product (i.e. a beer).