Ordinal Theory:

A Short Note In ordinal approach, utility is measured ordinally i.e., qualitatively (not numerically or quantitatively). Alternatively, consumer can rank her preferences according to the order she wants to compare but not in terms of the different amount. It's a qualitative measure and therefore more realistic measurement of utility or satisfaction. There are two different approaches of ordinal theory, viz.,

1) Indifference curve approach 

2) Revealed preference approach 

Indifference Curve Approach:

Indifference curve is constructed by taking utility level constant, so different indifference curves imply  different level of utility for same consumer. The equilibrium is achieved when indifference curve become tangent to the budget line. 

Revealed Preference Approach:  In revealed preference approach, consumer equilibrium can be found by ranking different bundle of goods in the commodity space. Given the budget constraint, consumer chooses the best bundle for which her utility will maximise. This theory was originally constructed by the famous economist Paul. A. Samuelson.