Proportionality

For the corresponding concept related to ratio, see Proportions.

A proportionality relationship happens when two quantities or numbers x and y are related multiplicatively by a fixed number. This can occur when either their ratio x/y is a fixed number (direct proportionality), or their product xy is a fixed number (inverse proportionality). If x is directly proportional to y, then we write ${\displaystyle x\propto y}$.^[1] The fixed number of a proportionality relationship is called the constant of proportionality.^[2][3]

Related pages

• Relation (mathematics)
• Function (mathematics)