7. Demand
1.      Meaning
Demand is a desire backed by ability to pay and willingness to buy a particular commodity.

2.      Limitation
Thereare number of limitations affecting demand such as ability to pay, willingness to buy, taste, preferences and habit etc.  

3.      Price Relation
Demand has inverse relationship with price.

4.      Examples
A desire to buy a Mercedes car by a rich man can be transferred into demand as he has the ability to pay and also willingness to buy.

A desire is a wish or an ambition to have something. It need not be backed by ability to pay.

There are no limitations for a desire. Any one can desire anything at any point of time. For ex. A beggar wants to go to the moon.

Desire does not have any relation with the price.

A poor man may also desire to have a Mercedes car, but it can not be transferred into demand, as he does not have the ability to buy.