the center in Math means that all the points on the outside of the circle go to the center of the cirlce
orgin
what does key mean in math
The distance from the center of a circle to its perimeter
Approximately
about
a
I do not know of such a word related to math(s)
There is no such math word, so it does not mean anything. You may wish to check your spelling before posting questions!
The circles are "concentric".
The word at means the least
the word by means 'times' or 'multiply'