In physics, resonance 's the tendency of a system to oscillate at larger amplitude at some frequencies than at others. These are known as the system's resonance frequencies (or resonant frequencies). At these frequencies, even small periodic driving forces can produce large amplitude vibrations, because the system stores vibrational energy. When damping's small, the resonance frequency's approximately equal to the natural frequency of the system, which's the frequency of free vibrations. Resona… (More on Resonance)