A curve formed by co-ordinates that when multiplied produce the same value. In micro economics the p/q combinations taken from a demand curve formed by co-ordinates exhibiting these properties will always produce the same amount of revenue and exhibit PED of -1 (unitary elasticity). As revenue is constant at all points on the curve it is not possible to achieve a higher amount of revenue by changing price or output.
Below is an example of this type of curve to represent the typical downward sloping demand curve. In this instance the same law of demand applies but it's just that the relationship between price and quantity demanded is unit elastic at all levels.
