Marginal Rate of Substitution :
According to Leftwich "The Marginal Rate of Substitution of x for y (MRS) is defined as the maximum amount of Y the consumer is willing to give up for getting an additional unit of X and still remaining on the same indifference curve."

According to Stonier and Hague :
"Demand in Economics means desire backed up by enough money to pay for the good demanded".

Criticism made on 'Consumer's Surplus' :
(i) Utility cannot be measured because utility is subjective.
(ii) Marginal Utility of money does not remain constant.
(iii) Potential price is internal, it might be known to the cons

Consumption is defined as "The use of goods and services for satisfying wants."

Price line (or) Budget line is represented by set of indifference curve depends on his money income and price level.

Consumption is defined as "the use of goods and services for satisfying wants". Consumption is the beginning of economic science. In the absence of consumption there is no production', exchange or distribution. Consumption is also an end of production.

(i) Perfectly Elastic Demand (E_p = \(\infty\))
(ii) Perfectly Inelastic Demand (E_p = 0)
(iii) Relatively Elastic Demand (E_p > 1)
(iv) Relatively Inelastic Demand (E_p < 1)
(v) Unitary Elastic Demand (E_p = 1)

Indifference map refers to a set of indifference curves corresponding to different income levels of satisfaction.

Budget line is a line showing different combinations of two goods which a consumer can attain at his given Income and Market price of the goods.

(i) Giffen goods: Sir Robert Giffen explained the exceptional nature of inferior goods. So these inferior goods (eg) ragi are called Giffen goods.
(ii) When the price of an inferior good falls, the poor will buy less and vice versa.
(iii) It is an exception to the law of demand.

(i) Consumer's surplus = potential price - actual price (or)
(ii) Consumer's surplus = what a person is willing to pay - what he actually pays (or)
(iii) Consumer's surplus = TU - (P x Q)

An indifference curve is the locus of different combinations of 2 commodities which gives the consumer the same level of satisfaction.

(i) Cardinal approach of Marshall- utility is measured by cardinal numbers such as 1,2,3
(ii) Ordinal approach of Hicks and Allen- utility can be compared or ranked or ordered such as I,II,III.

(i) Want satisfying power of a commodity is called utility.
(ii) It is measured in utils.