Definition:Divisor (Algebra)/Real Number/Part

Definition

A more old-fashioned term for divisor is part:

In the words of Euclid:

A magnitude is a part of a magnitude, the less of the greater, when it measures the greater.

(The Elements: Book $\text{V}$: Definition $1$)

The alert student will notice the circular definition: a part is defined in terms of measuring another quantity, and measurement is defined in terms of a divisor, that is, a part.