What is critical rpm and super critical rpm?

Critical RPM (Revolutions Per Minute) refers to the speed at which a rotating system's natural frequency coincides with its rotational frequency, leading to resonance and potentially excessive vibrations. Supercritical RPM is the speed beyond the critical RPM where the system operates safely and stably, typically resulting in a reduction in vibration amplitudes as the frequency increases past the resonance point. In engineering, understanding these RPMs is crucial for designing machinery to avoid operational failures and ensure longevity.