Definition of: resonance

(rez′ə·nəns) noun
1. The state or quality of being resonant; resonant sound.
2. Physics a The phenomenon exhibited by any vibratory system responding with large amplitude to a series of imposed vibrations of equal, or nearly equal, frequency. b That property of a molecule by virtue of which it assumes an electronic structure intermediate between two other theoretically possible structures. c The prolongation and amplification of sound by reverberation within a cavity.
3. Electr. The condition of an electric circuit in which maximum flow of current is obtained by impressing an electromotive force of given frequency. [<L resonantia echo]