Demand - The quantity of a commodity which a consumer wish to purchase at given price and given period of time is called demand.

Market demand- The quantity of a commodity which all the consumers in the market wish to purchase at a given price and given period of time is called market demand.

Determinants of demand- The main determinants of demand for a commodity are as follows

i) Price of the commodity- When the price of a commodity increases the demand for that commodity decreases and vice versa. It means there is inverse relationship between price of commodity and quantity demanded.

ii) Income of the consumer - The income of consumer affects the demand of commodity as follows

The demand for normal goods tends to increase with increase in consumer income and vice-versa. On the other hand, the demand for inferior goods tends to decrease with increase in consumer income and vice-versa.

iii) Taste and preferences- When taste and preferences are in favour of the commodity demand for commodity increases and vice versa.

iv) Future expectation of change in price of good- If it is expected that price of commodity will increase in future ,consumer starts purchasing the commodity more at present. Therefore demand of commodity increases at present and vice versa. 

v) Price of related goods - The related goods are of two types- complementary goods (The goods which are used together) and supplementary good (The goods which are used in place of each other).

In case of complementary goods, demand of a good rises with fall in price of complementary good and vice versa. In case of supplementary (substitute) goods, demand of a good falls with a fall in the price of other substitute goods and vice versa.

The above five factors affect the individual demand. But for market demand some more factors including above are as under -

vi) Government policy - When government increases the tax on a particular commodity, the commodity become costlier, so less number of consumers will purchase the commodity. Hence demand of commodity decline and vice versa.

vii) Population- With increase in population of a country demand for commodity rises. However, if the population is decreasing, then demand will fall.

viii) Climate - If climate of an area is favourable for the consumption of a good then demand for the good will be more and vice versa.