What is demand?

What is demand?
Demand is something which you are willing and able to buy. A mere desire to buy something is not a demand.
For example:
A man has $1000
A car is worth $4000
A motorcycle is worth $950
If the buyer wants to buy a car, it will only be considered to be a desire as he is willing to buy the car but he is not able to buy the car because he has $1000 and the car is worth $4000
If the buyer wants to buy a car, it will be considered to be a demand as he is willing and able to buy the motorcycle. The motorcycle is worth $950 and he has $1000.