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amplitude (of vibration)
(degree of) instability; volatility; fluctuation; variation; swing
音波の振幅を調べた。
I measured the sound wave amplitude.
弦の振幅が減って音が消えた。
The string's amplitude decreased and the sound died out.
バネを強く引くと振幅が大きくなる。
Pulling the spring hard makes the amplitude larger.