A product often used together with another product is called what?

• A. Complement
• B. Substitute
• C. Normal Goods
• D. Inferior Goods

Answer: (A)

When goods are regularly used together, they are called complements. The idea is that the demand for one product is linked to the demand for the other because they enhance each other’s usefulness. For example, printers and ink cartridges or tea and sugar are often bought together, so a fall in the price of the printer can raise demand for ink cartridges, and a rise in the price of one can lower demand for the other.

This differs from substitutes, which are goods that can replace each other in consumption; if the price of one goes up, people switch to the other. Normal and inferior goods relate to how demand changes with income, not whether they’re used with another product.

So the term that matches “a product often used together with another product” is a complement.