Definition
Hemisphere
A solid hemisphere is half of a sphere cut through its centre.
What it means
Imagine slicing a ball exactly through its centre. Either half is a hemisphere. The cut makes a flat circle, while the outside keeps half of the ball’s curved surface.
Remember it
Hemi means half: half a ball plus a flat circle.
Example
A solid sphere of radius 6 cm is cut through its centre. Each piece is a hemisphere with a circular base of radius 6 cm and a height of 6 cm.
Watch for
A shallow dome cut above the sphere’s centre is a spherical cap, not a hemisphere.
Common mix-up
A semicircle is half of a 2D circle; a hemisphere is half of a 3D sphere.
Exact meaning
A solid hemisphere is one of the two congruent solids formed when a solid sphere is cut by a plane through its centre. It has one flat circular base and one curved surface.