Definition:Corresponding Magnitudes

Definition

Let $R_1 = a : b$ and $R_2 = c : d$ be ratios.

Then the corresponding magnitudes of $a$ and $b$ in $R_2$ are $c$ and $d$ respectively.

In the words of Euclid:

The term corresponding magnitudes is used of antecedents in relation to antecedents, and of consequents in relation to consequents.

(The Elements: Book $\text{V}$: Definition $11$)