When two ratios are equal, then it is

The correct answer is: Proportion

Ratio and proportions are said to be faces of the same coin. When two ratios are equal in value, then they are said to be in proportion. In simple words, proportion compares two ratios.
 In simple words, it compares two ratios. Proportions are denoted by the symbol ‘::’ or ‘=’. Two ratios a:b and c:d are proportional if they are equal, i.e., .
Thus, when two ratios are equal, then it is proportion.