Goods which are used together, so a reduction in the price of one leads to an increase in demand for the other....more on complementary goods
Complementary goods are consumed at the same time e.g. cars and petrol. Therefore an increase in the demand for one will cause an increase in the demand for the other. An indication of the goods being complementary is the cross price elasticity of demand. If the CPED is negative then the two goods are complements. If the value is greater than one, ...
Complementary goods are products that may be used together with other products that enhance their features.