A ______ is a ratio that compares two quantities.

A rate is a specific type of ratio that expresses the relationship between two quantities, typically with different units of measurement. For example, a common representation of a rate can be seen in speed, which relates distance to time (miles per hour). Rates allow for the comparison of variables and provide meaningful insights into their relationship.

In contrast, a proportion involves the equality of two ratios, showcasing how one part relates to another as a fraction of a whole. A percentage represents a ratio expressed as a fraction of 100, which can be seen as a special case of a rate but is used specifically to describe parts per hundred. Value, in a more general sense, refers to the worth or importance of something and does not inherently indicate a comparison between two quantities. Hence, the term that best fits the definition of comparing two distinct quantities is a rate.