A constant of variation, also known as a constant of proportionality, is a non-zero constant that relates two variables.

Direct Variation

In a direct variation, the constant of variation $k$ represents the ratio of two variables. The ratio remains unchanged when the variables $x$ and $y$ change. When the variable $y$ is isolated on the left-hand side, the constant of variation $k$ defines the slope of the line through the origin that represents the relationship between $x$ and $y.$

Inverse Variation

In an inverse variation, the constant of variation $k$ is the product of two variables. The product remains the same when the variables $x$ and $y$ change.