Joint DemandWhen two or more goods are demanded to satisfy the same want, it is called JOINT DEMAND. A good example of joint demand would be a demand for sugar, coffee powder and milk to produce coffee. Another example can be a demand for car and petrol to fulfill the same desire, i.e transport. Note that the goods demanded are not substitutes for each other, but complement each other.
Composite DemandWhen a particular commodity is demanded to be put to multiple uses, it is called COMPOSITE DEMAND.
An example of composite demand is the demand for water, which can be put to uses such as cooking, cleaning, drinking, etc. Demand for cow can also be considered composite demand, as the hide, milk and meat are all useful to a consumer