Straight lines in a circle are said to be *equally distant* from the center when the perpendiculars drawn to them from the center are equal.

And that straight line is said to be at a *greater distance* on which the greater perpendicular falls.

These definitions could have been broadened to distances from a line to an arbitrary point, but Euclid’s needs only distances from a line to the center of a circle.
The perpendiculars As the perpendicular |