General:
* Sphere: (n.) A round, three-dimensional object, like a ball.
* Spherical: (adj.) Shaped like a sphere.
* Spheroid: (n.) A slightly irregular sphere.
Scientific:
* Hemisphere: (n.) Half of a sphere.
* Geosphere: (n.) The solid, rocky part of the Earth.
* Biosphere: (n.) The part of Earth where life exists.
* Atmosphere: (n.) The layer of gases surrounding Earth.
* Hydrosphere: (n.) All the water on Earth.
Other:
* Sphere of influence: (n.) An area in which a person, group, or country has a lot of power.
* Sphere of activity: (n.) The range of things that a person, group, or organization does.
* Stratosphere: (n.) A layer of Earth's atmosphere.
* Lithosphere: (n.) The rigid outer part of the Earth, including the crust and upper mantle.
These are just a few examples, and there are many more words that use "sphere" as a root.