Amplitude is the maximum displacement of a particle from its mean position within a wave. This displacement can be measured above or below the mean position, depending on the direction of the wave's oscillation.

Here's a breakdown:

* Mean position: The average position of a particle when there is no wave disturbance.

* Displacement: The distance a particle moves from its mean position.

* Amplitude: The maximum displacement, whether positive (above the mean) or negative (below the mean).

Think of it like a swing. The mean position is when the swing is hanging straight down. The amplitude is the maximum height the swing reaches on either side of this mean position.