What is a direct proportionality?

Direct proportionality refers to a relationship between two variables where an increase in one variable results in a proportional increase in the other variable, and vice versa. Mathematically, this can be expressed as ( y = kx ), where ( k ) is a constant of proportionality. In this relationship, the ratio of the two variables remains constant, meaning that if one variable doubles, the other also doubles. This concept is commonly seen in physics and economics, among other fields.