What are goods known as when they are demanded together?

When goods are demanded together, they are referred to as complements. This relationship occurs when the demand for one good increases the demand for another good because they are often used together. A classic example would be peanut butter and jelly; when someone buys peanut butter, they are likely to also purchase jelly, leading to a combined demand for both products.

The concept of complementary goods illustrates how the consumption patterns of one product can influence another, highlighting the interdependence within markets. This is important for businesses as they can strategize marketing and pricing based on the knowledge of such relationships.

The other options pertain to different types of goods. Substitutes are goods that can replace each other in consumption. Luxury goods are those for which demand increases as consumer incomes rise, while inferior goods are those for which demand decreases as incomes increase. None of these concepts relate to the idea of goods being demanded together.