Answer: able to perform the same function as
Explanation:
Substitute products or services must be able to perform the same function as the industry's offerings.
For a good to be considered a substitute good, it needs to be able to serve the same function as the rest of the industry's offerings. This way, if people decide that they do not want a particular product, they could switch to the substitutes.
For instance, two very famous substitutes would be Pepsi and Coke. They both serve the same function and so are substitutes. If you start demanding less of Pepsi, you could demand more of Coke.
