A product line is a group of products that are closely related, either because they serve a similar purpose or because they are marketed together. For example, a company that makes and sells breakfast cereal might have a cereal product line that includes several different types of cereal, such as oatmeal, corn flakes, and bran flakes.
In business, a product line is often used to refer to a group of products that a company offers for sale. A product line can include products that are physically similar, such as a line of clothing, or products that are different but serve a similar purpose, such as a line of cleaning products. A product line can also include products that are related because they are marketed together, such as a line of toys that are all based on a particular character.