Translation:A circle does not have only one radius.
This seems like a very odd thing to say, though it is technically correct. On a diagram of a circle you can have more than one radius. I think the reason why this sounds so strange to me is that a radius on a diagram is quite different from the measure of a radius (which is the the same for all the radii in a circle by definition), which is frequently just called 'the radius' in English. I found it a very confusing sentence to translate into English for this reason.
No, I am still puzzled. If you start from the center of a circle and measure outward you get the radius. You can do this numerous times, but the result will always be the same. These aren't varying radii, but the same radius. A circle really can only have one radius. But hey, I am here to practice Greek, even if the logic is a little wonky
English usage is imprecise between "the line that passes through the centre of the circle and stops at the circumference" and "the length of that line". The former is what is meant in the example sentence here; the latter is what you mean.