Direct proportion is a relationship between two quantities where an increase in one quantity results in a proportional increase in the other. For example, if x is directly proportional to y, then when x doubles, y also doubles. This relationship can be expressed mathematically as y = kx, where k is a constant. In practical terms, direct proportion can be seen in everyday situations, such as when buying fruit. If the price of apples is $2 per pound, then buying 3 pounds will cost $6. Here, the cost is directly proportional to the weight of the apples purchased.