Substitute

What Does Substitute Mean?
A product or service that partly satisfies the need of a consumer that another product or service fulfills.

Investopedia explains Substitute
For a product to be a substitute of another good, it must share a particular relationship with that good. When a good's price increases, the demand for its substitute will increase because consumers will go looking for a cheaper alternative. Conversely, when a good's price decreases, the demand for its substitute will decrease. For example, margarine is a substitute for butter because a consumer can meet similar needs by using margarine. So, when the price of butter rises, the demand for margarine will also likely increase.