# Single Responsibility Principle The Single Responsibility Principle is the "S" in the [[solid principles|SOLID]] acronym. In short, this principle says a class should have one reason to change. But what does that mean exactly, and what does it look like in practice? When a class handles too many concerns—like generating a report, saving it, and printing it—modifying one part can break another. Splitting responsibilities into focused classes leads to clearer, safer designs.