Glossary:Q factor
The Q (or quality) factor of a resonant system, such as a tuned circuit, a quartz crystal, a guitar string or a pendulam, is a measure of how free it is to resonate at its natural frequency. It can be defined in terms of the sharpness of the resonant frequency, or as the number of times greater the stored energy of the resonator is than the energy lost per vibration or cycle. For example, a tuning fork which rings for a long time after being struck, is exhibiting a high Q due to minimal losses.