In science, how far a wave swings away from its resting middle line — measured from the middle to the top of the wave, not from the bottom to the top. It is the size of the swing, not how often the swing happens (that is frequency).

In science在科學上, how far a wave swings away from its resting middle line指的是一個波偏離它靜止中線的幅度 — measured from the middle to the top of the wave是從中線量到波峰, not from the bottom to the top不是從波谷量到波峰。It is the size of the swing它指的是擺動的大小, not how often the swing happens (that is frequency)不是擺動發生的頻率（那是 frequency）。

This one measurement explains a lot: for sound, bigger amplitude means louder; for light, it means brighter; for a swinging rope or a pendulum, it means a wider swing. So when a teacher says 'turn it up', in physics language you are raising the amplitude.

This one measurement explains a lot這一個測量值能解釋很多東西: for sound, bigger amplitude means louder對聲音來說，振幅越大代表越大聲; for light, it means brighter對光來說，代表越亮; for a swinging rope or a pendulum, it means a wider swing對擺動的繩子或鐘擺來說，代表擺動的幅度更大。So when a teacher says 'turn it up'所以當老師說 'turn it up'（調大聲一點）, in physics language you are raising the amplitude用物理的說法就是在提高振幅。

There is also an older, grander, non-scientific use meaning 'largeness, plenty, wide range' — 'the amplitude of his knowledge' — but that one is formal and literary, and you will meet it in old books more than in speech. In exams and textbooks, take it as the wave measurement.

There is also an older, grander, non-scientific use還有一個比較古老、比較宏大、非科學的用法 meaning 'largeness, plenty, wide range'意思是「宏大、豐富、範圍廣」 — 'the amplitude of his knowledge'像 'the amplitude of his knowledge'（他學識的淵博） — but that one is formal and literary但這個用法很正式、偏文學, and you will meet it in old books more than in speech比較會在舊書裡碰到，而不是在口說裡。In exams and textbooks, take it as the wave measurement在考試和課本裡，把它當成波的測量值來理解就好。