A hemisphere is a 3-d shape and so does not have a name as a 2-d shape.
2-d sections of a hemisphere can be circles, semicircles, or sections of circles, depending on the inclination of the intersecting plane.
The 2D shape of a hemisphere is a semicircle. When you take a hemisphere, which is half of a sphere, and project it onto a flat surface, it creates a semicircle, representing the curved surface. The flat side of the hemisphere corresponds to a straight line, completing the shape. Thus, the 2D representation of a hemisphere is a semicircle plus a diameter.
A 2D shape with 9 sides is called a Nonagon.
Hexagon
A pentagon
Octagon
The 2D equivalent of a sphere is a circle so it follows that the 2D equivalent of a hemisphere is a semicircle.
A hemisphere is a three dimensional shape that is essentially the same as half of a sphere.
A semi-circle.
A 2D shape with 9 sides is called a Nonagon.
Octagon
2D shapes include squares, triangles, rectangles and circles.
Square
hexagon
Hexagon
Tetradecagon.
A pentagon
Octagon