Final answer:
The statement refers to the 'law of demand,' which describes the inverse relationship between the price of a good or service and the quantity demanded by consumers.
Step-by-step explanation:
The statement "the quantity demanded of a product varies inversely with its price" defines the law of demand. This law indicates that there is a common relationship where a higher price for a good or service leads to a lower quantity demanded, and conversely, a lower price leads to a higher quantity demanded. Price, the amount a buyer pays for a unit of goods or services, and quantity demanded, the total number of units that consumers are willing to purchase at that price, are inversely related as per this economic principle. The law of demand holds true assuming all other variables that affect demand remain constant.