Definition of Demand

The demand for any commodity at a given price is the quantity of it which will be bough per unit of time at that price.

This definition underlines two important things. First, demand is always at a price. If we say demand for fish in market is 5 quintals, it is meaningless. When it is said that demand for fish in market is 5 quintals when the price per kg. Of fish is $1, it becomes reasonable. Secondly, demand must be referred to a time period, say a day, a week or a month. In the above example when we say that demand for fish in market is 5 quintals per day when price per kg. of fish is $1, it gives us a complete meaning of demand.