10.            joint demand
composite demand
1.      Meaning
When two or more commodities are demanded at the same time to satisfy a single want, it is called as joint demand.

2.      Examples
      Joint demand can be for car and petrol, or for socks and shoes, or for pen and paper, or tea and milk, or for mobile and sim card.

When a single commodity is demanded to satisfy several wants. It is called as composite demand.

Electricity has composite demand, s it can be used for several purposes such as lighting, heating, manufacturing, cooking. Etc. (water also)