Astronomers call a system composed of more than two stars a multiple star system or multi-star system.

Here's why:

* Clarity: The term "multiple" or "multi" clearly indicates the presence of more than two stars, avoiding any ambiguity.

* Specificity: It distinguishes these systems from binary stars, which are specifically composed of two stars.

* Generalization: It encompasses all systems with more than two stars, regardless of the exact number (e.g., triple star, quadruple star, etc.).

While sometimes specific terms like "triple star" or "quadruple star" are used, "multiple star system" remains the most common and general designation for systems with more than two stars.