Definition:Coprime/Integers/Relatively Composite

Definition

Let $a$ and $b$ be integers such that $b \ne 0$ and $a \ne 0$ (i.e. they are both non-zero).

Let $\gcd \set {a, b}$ be the greatest common divisor of $a$ and $b$.

If $\gcd \set {a, b} > 1$, then $a$ and $b$ are relatively composite.

That is, two integers are relatively composite if they are not coprime.

In the words of Euclid:

Numbers composite to one another are those which are measured by some number as a common measure.

(The Elements: Book $\text{VII}$: Definition $14$)