its called a Radius
The curved line that traces the boundary or perimeter of a circle is called the circumference. A straight line that touches the circle at just one point is called a tangent. See the related link, 'The Parts of the Circle', below this answer.
The diameter of a circle is a straight line going from one point on its boundary, through the centre of the circle, to the boundary on the other side.
Not at all! The circumference is the length of the boundary of a circle. A chord is a straight line(or a line segment) that passes through two points on the boundary of a circle (or on a curve).
The radius of a circle is a line segment joining any point of the boundary of the circle to its centre. A diameter is a line segment from a point of the boundary of the circle which passes through the centre and ends at the boundary on the opposite side.
The boundary or perimeter of a circle is called the circumference. The formula for calculating the length of the circumference is C = 2πr.
It is an "open" circle. That is, a circle which is not filled in.
The boundary line under the basket is known as the baseline.
Depends on the context: London has a tube (Metro) line which is called the Circle Line.
The diameter of a circle is a straight line going from one point on the circumference (the boundary) of the circle, through the centre of the circle, to another point on the circumference.
This is a line segment called a diameter of the circle.
A diameter is a straight line from one side of a circle, through the centre, to the other side. A circumference is the curved line forming the boundary of a circle.