Answer: Utility function .
Explanation: In economics and particularly in consumer choice theory, the substitution effect is one component of the effect of a change in the price of a good upon the amount of that good demanded by a consumer, the other being the income effect .
utility function is an important concept that measures preferences over a set of goods and services. Utility represents the satisfaction that consumers receive for choosing and consuming a product or service. Utility is measured in units called utils, but calculating the benefit or satisfaction that consumers receive from is abstract and difficult to pinpoint. As a result, economists measure utility in terms of revealed preferences by observing consumers' choices. From there, economists create an ordering of consumption baskets from least desired to the most preferred.
utility function measures the welfare or satisfaction of a consumer as a function of consumption of real goods such as food or clothing. Utility function is widely used in the rational choice theory to analyze human behavior.
When economists measure the preferences of consumers, it's referred to ordinal utility. In other words, the order in which consumers choose one product over another can establish that consumers assign a higher value to the first product. Ordinal utility measures how consumers rank one product versus another.
Economists take the utility-function concept one step farther by assigning a numerical value to the products that consumers choose or choose not to consume. Assigning a value of utility is called cardinal utility, and the metric used to it is called utils.
For example, in certain situations, tea and coffee can be considered perfect substitutes for each other, and the appropriate utility function must reflect such preferences with a utility form of u(c, t) = c + t, where "u" denotes the utility function and "c" and "t" denote coffee and tea. Economists might conclude that a consumer who consumes one pound of coffee and no tea derives a utility of 1 util.
