amplitude

Definitions

ampl (large) + -itude (state of being) = 'the state of being large,' i.e. extent or size. Physics borrowed this general 'largeness' word for a precise idea: how far a wave swings from its resting point. A loud sound or bright light is just a wave with high amplitude.

Why It Means This

Amplitude started as a plain word for 'largeness' or 'breadth' (you can still say someone has 'amplitude of mind'). Then physics gave it a sharp technical meaning: on a graph of a wave, amplitude is the height of the crest above the centre line. This is why turning up the volume increases a sound wave's amplitude, not its frequency. Keep amplitude (how big the swing) separate from frequency (how often it swings) and from magnitude (overall size).

Common Collocations

• 1.wave amplitude波幅
• 2.amplitude modulation调幅
• 3.high amplitude高振幅
• 4.low amplitude低振幅

Example Sentences

• 1.

  The amplitude of a sound wave determines how loud we perceive it to be.

• 2.

  Engineers measured the amplitude of the bridge vibrations during the storm.

Easily Confused

amplitude vs magnitude vs frequency — All describe 'how much' of a wave or quantity. Amplitude is the size of the swing from rest (volume of a sound). Frequency is how many swings per second (pitch of a sound). Magnitude is overall size or strength (the magnitude of an earthquake). Swing height → amplitude; swing speed → frequency; total size → magnitude.