__Ratio:__

A ratio shows the relative sizes of two or more values. Ratios can be shown in different ways. Using the ":" to separate example values, or as a single number by dividing one value by the total.

__Proportion:__

A part, share, or number considered in comparative relation to a whole. Proportion says that two ratios (or fractions) are equal. Eg: 1/3 = 2/6

__Variation:__

A relationship between two variables in which one is a constant multiple of the other. In particular, when one variable changes, the other changes in proportion to the first. If b is directly proportional to a, the equation is of the form b = ka (where k is a constant).