Final answer:
The phrase in question refers to the economic concept of substitution, where a good or service can be replaced by another. This can happen due to price changes, like with tablets and laptops, or due to the availability of alternatives, like e-books versus printed books.
Step-by-step explanation:
The phrase used when a substitution is permitted for a specific item refers to the ability of one good or service to be replaced by another, particularly in the context of market demand and consumer choice. A common example of substitution in economics is when consumers opt for tablet computers over laptops due to a price decrease in tablets, leading to an increase in tablet demand and a decrease in laptop demand. This phenomenon can be depicted graphically through a shift in the demand curve.
Another example of substitution can be seen as printed books versus electronic books. With the availability of e-books, the demand for printed books tends to decrease. If substitution occurs because of price, the law of demand indicates that a lower price for the substitute (e.g., tablets) decreases demand for the alternative product (e.g., laptops).