Final answer:
The use of the same brand name within the same product line is known as a line extension, such as introducing new flavors of toothpaste under an existing brand.
Step-by-step explanation:
The use of the same brand name within the same product line is referred to as a line extension. This strategy involves adding new products to an existing product line under the same brand name. For example, if a company produces toothpaste and it decides to introduce new flavors or formulas, like whitening or tartar control, under the same brand, this would be considered a line extension.
Other options, like brand extension, involve using the brand to enter a different product category altogether. Brand dilution occurs when a brand loses its strength due to overextension or poor management, and co-branding involves a partnership between two brands to create a new product.