Possibly the conversion factor.
A ratio between two sets of measurements is called a proportion. A proportion is a statement that two ratios are equal. It is often used to compare quantities or values in different contexts, such as in mathematics, science, and finance. The relationship between the two sets of measurements can be expressed using fractions or decimals.
The ratio is the same as the ratio between the number of teeth.
Cross Products
There is no real reason for two equivalent measurements to be rationed! The ratio of two equivalent measurements will depend on the units used. The ratio between a length in feet and the equivalent length in inches, for example, is 12:1.
an example of a ratio is the difference between two numbers or sets of numbers such as 600 and 200... the ratio is 400...