When the wave caused the term occurs: particles of the medium move from the original position (called displacement) by this term when it comes to the most remote locations in the period we are called the amplitude.
When the waves come up to the stage where the particles of the medium move from its original location (called the displacement), the distance to this. Upon arrival in the distance. Time, we are called Amplitude.
When a wave, happen to be born while the particles of the medium is moving from the original position (called displacement) by stage that this Upon arrival in the far distance, we called the amplitude.