Semi circle
another name for a half circle is semi-circle
Each meridian is a half-circle from the north pole to the south pole of the earth.
Another name for half a circle is a semicircle.
It is a semi-circle
The Equator is the line that separates the earth into two hemispheres
hemisphere
There is no specific name.
The circumference
depends on the information given, but radius is half of the diameter.
The perimeter of a circle is its circumference
Circumference.
Circumference.