The radius of a circle is half of its diameter
Half a circle is called a SEMI-CIRCLE
Half a circle is called a semi-circle. Sometimes it is called a half-moon.
A half circle is called a semicircle.
semicircleA half circle is called a semicircle.Half a circle is a semi-circle
In geometry it is called the "Great Circle".
If you are referring to geometry, half the diameter = the radius. For example the radius of a circle is half it's diameter
Semi = half
half of the radius the radius is half of the diameter the diameter is the with of the circle. This also can be called a quadrent circle.
Half the diameter of a circle is called its radius.