Define or explain the following concept:
When goods are demanded so that they can be used in the production of some other commodity, it is called indirect or derived demand. Thus, in such cases the demand for a commodity is dependent on the demand for the commodity in the production of which it would be used. For instance, when wood is demanded for making furniture, wood is said to have derived demand. As the demand for furniture increases, the demand for wood also increases and vice-versa.