 market demand is equal to market supply. But if market is not in equilibrium, then market demand is not equal to market supply. And when market demand is not equal to market supply, then we say market is in disequilibrium. When we say market is in disequilibrium, then what situation can be? It might be possible market demand is greater than market supply. If market demand is greater than market supply, at a particular price, you can say there is shortage. And then on the same pattern, if market demand is less than market supply, you can say at that particular time, there is surplus in the market. And in the market you have surplices where the shortage is observed. When if market demand is not equal to market supply. Now to elaborate on this, again we are taking an agricultural commodity here. What agricultural commodity is it? Suppose we are taking quantity of vegetables on horizontal axis and price on vertical axis. And the downward sloping curve, I am denoting the demand for vegetables. And S curve is denoting the supply for vegetables. And what is market equilibrium price? PE and equilibrium quantity is QE. This is the price and quantity where demand is equal to supply. If I talk like this, suppose if price is equal to PA, price is above to the equilibrium price. Now in this particular situation, if price is equal to PA, supply of vegetables is equal to SA. And here the demand for vegetables is DA. Now if I compare quantity, demand and quantity of the supply against price, then I can observe one thing that I have less quantity demand as compared to supply. I say supply of vegetables is greater than demand for vegetables is equal to price PA. If supply is greater than demand, then there is a surplus. Whenever there is a surplus in the market, what will you do? It will create a downward pressure on the prices, on the price of the commodity. Because of decreasing supply, decrease in price, your supply will decrease. Because of downward pressure on the prices, when prices decrease, demand will increase. Ultimately our system will move towards equilibrium. If I collaborate with reference to shortage, when is shortage? Again on the same pattern, we have an original demand and supply. If I assume price of vegetables in the market is equal to PB. What is the demand for vegetables? It is equal to DB quantity of vegetables. What is the supply of vegetables? It is equal to SB. If I compare quantity, demand and quantity of the supply, then what is the indicator? This price B, quantity demand for vegetables is greater than the quantity supply of vegetables. When quantity demand for vegetables is greater than quantity supply of vegetables, it indicates there is a shortage. When there is a shortage, because of shortage, it will create an upward pressure on the prices of vegetables. When the prices of vegetables increase, there is increase in supply and at the same time, there is decrease in quantity demand for vegetables. Ultimately our system will move towards a point where demand is equal to supply. If I summarize these two things, if our market is not in equilibrium, then there are two types of situations. Here there will be a shortage or a surplus. This shortage or surplus is not a permanent feature. Ultimately our system will move towards market equilibrium and this is the point where demand is equal to supply.