Why is the ninth month called September?
mid-15c., in acoustics, "prolongation of sound by reverberation;" 1660s, "act of resonating;" from Middle French resonance (15c.), from Latin resonantia "echo," from resonare "to sound again" (see resound). Earlier in same sense was resonation (early 15c.).
resonance res·o·nance (rěz'ə-nəns)
The sound produced by diagnostic percussion of the normal chest.
Intensification of vocal tones during articulation, as by the air cavities of the mouth and nasal passages.
Intensification and prolongation of sound produced by sympathetic vibration.
The property of a compound having simultaneously the characteristics of two or more structural forms that differ only in the distribution of electrons.
Oscillation induced in a physical system when it is affected by another system that is itself oscillating at the right frequency. For example, a swing will swing to greater heights if each consecutive push on it is timed to be in rhythm with the initial swing. Radios are tuned to pick up one radio frequency rather than another using a resonant circuit that resonates strongly with the incoming signal at only a narrow band of frequencies. The soundboards of musical instruments, contrastingly, are designed to resonate with a large range of frequencies produced by the instrument. See also harmonic motion.