* Definition of a Star System: A star system is a group of two or more stars that are gravitationally bound to each other.

* Binary Stars: Binary stars are a specific type of star system where two stars orbit a common center of mass.

Therefore, since binary stars are two stars orbiting each other, they inherently form a star system.

It's important to note:

* Multiple Star Systems: While binary systems are the most common, there are also trinary (three stars), quaternary (four stars), and even larger multiple star systems.

* Exoplanets: Star systems can also include planets, moons, asteroids, and other celestial objects that orbit the stars.

So, whenever you hear "binary star," you can safely assume it's referring to a system of two stars gravitationally bound together.