What is Demand, factors affecting demand or determinants of demand

What is Demand?
Demand is willingness to purchase and financial ability to purchase goods and services at given a price and a certain period of time is known as demand.
When we talk about demand first thing comes under our thought is who creates demand? The answer is consumer. Demand can be created through 2 things first we need willingness to purchase and secondly we need money to purchase that commodity. If we lack any of requirity it will not be called as demand. For example:- suppose a beggar want roti but he can’t purchase it so, it means he is not creating demand.
Factors affecting Demand 
Demand of a consumer can vary in response to several factors like price of own commodity, income of consumer, taste and preference, size of population, etc. It is represented by

Dx=f(Px,Py,Y,T,.....) 

Here Px represent price of commodity, Py represent price of related good, Y represent income of consumer and T represent taste and preference of consumer. These are the factors which affect demand. 

Price of commodity:-Price of the commodity also also affect the demand of the commodity. If price of commodity rises then its demand will fall and if price falls then demand will rise. For example:- If the price of wireless mouse will increase from 10 then its demand will decrease and vice-versa. 

Price of related goods:-price of related good also affect demand of consumer. There are 2 types of related goods. 

          1.complementary goods:-complementary goods are those goods which are use together to satisfy a particular want for example:-pen and ink, car and petrol, tea and sugar, etc. If price of complementary good increases the demand for given commodity will fall and if price of complementary good falls then demand of given commodity will rise. For example:-If price of ink increase then people will reduce the demand of pen and vice-versa. 

          2.substitute goods:-Substitute goods are those goods which can be used in place of other goods for example:- pen and pencil, colgate and pepsodent, pepsi and coca-cola, etc. If price of substitute good increases then demand for given commodity increases and if price of substitute good decreases then price of given commodity decreases. For example:-If price of pepsi increases then people will substitute pepsi and start buying coca-cola hence demand of coca-cola will increase and vice-versa.

Income of consumer:-Income of consumer also affect the demand of consumer. If the income of consumer increases then demand for normal goods will increase and if income of consumer decreases then demand for normal goods will fall. 

Size of population:-if size of population is large then demand will increase and if size of population is small then demand will fall. 

Future expectation:-Future expectation also affect the demand. If price of a good is expected to increase in near future then its current demand will increase and If price of a good is expected to decrease in near future then its current demand will decrease.