Here's a breakdown:
* Sphere: A perfectly round three-dimensional object, like a ball.
* Hemisphere: A half-sphere, created by dividing a sphere in half along any plane that passes through its center.
Think of slicing a grapefruit in half - each half is a hemisphere.
Examples:
* Earth's hemispheres: The Earth is divided into the Northern Hemisphere and the Southern Hemisphere by the Equator.
* Brain hemispheres: The human brain is divided into two hemispheres: the left and right.
Let me know if you have any other questions!