"Directly proportional" describes a relationship between two variables where an increase in one variable results in a corresponding increase in the other. For example, if you double the amount of money you spend on groceries, the quantity of food you can buy also doubles, assuming prices remain constant. This means that the two variables change at the same rate. In mathematical terms, if x is directly proportional to y, it can be expressed as y = kx, where k is a constant. This relationship is often represented graphically as a straight line that passes through the origin, indicating that both variables are linked in a consistent manner.