What is the term for relating one quantity to another quantity?

The term that describes the relationship between one quantity and another quantity is known as a ratio. A ratio expresses how much of one thing there is compared to another, providing a clear comparison between two numbers. For example, if you have 2 apples and 3 oranges, the ratio of apples to oranges would be expressed as 2:3.

In contrast, while a rate is similar in that it compares two quantities, it often incorporates a unit of time or a specific measurement (like miles per hour). Random variation refers to unpredictable changes or fluctuations in data, which does not pertain directly to the relationship between two quantities. Regression analysis, on the other hand, is a statistical method used to determine the relationship between a dependent variable and one or more independent variables, but it is not simply the measure of relating two quantities directly.

Therefore, the term ratio is the most accurate description for relating one quantity to another.