The word from the list that best fits the definition of "repeating 'Why to buy' to remember the rules of supply and demand" is "rhyming." The term "Why to buy" is not a list of keywords or a set of rules, but rather a phrase that has been intentionally constructed to rhyme in order to aid in memory and recall. Rhyming can be a useful technique for helping to remember and recall information, as it can make the information more memorable and easier to recall through the use of a memorable and catchy phrase. In this case, "Why to buy" may have been created as a rhyming phrase to help remember the rules of supply and demand.