Abstract: Multiple connotations of the quality factor Q associated with frequency characteristic，energy conversion，and various physical variables are analyzed. The analysis is based on the differential equation of second-order system with sinusoidal excitation，as well as the physical contexts of forced damping vibration and RLC serial /parallel resonant circuits. Then it is also discussed that how to teach the concept of quality factor Q better for engineering students.

Key words: quality factor, damping vibration, resonant circuit