Å is a letter in the Swedish alphabet. The circle is part of the letter. It has no name to distinguish it as separate from the A. In Swedish, it's just an Å. It's name sounds like the O in Ohio.
The perimeter of a circle is its circumference
It's called a radius
circumference
That is called an "arc".
It is called a protractor.
The circle on top of an i is called a dot. That is why you hear teachers talk about dotting i's.
The center of a circle is called the origin. It is a point at one end of a radius, the other end of which defines the circumference of the circle.
I bi I believe it is called a Sphere
A chord. The longest possible chord is one that goes through the center of the circle. That has a special name ... it's called the 'diameter' of the circle.
It is called a cone.
It is just called a "central angle".
That's called the radius.