The measurement of a wave's magnitude oscillation is called its amplitude.

Here's a breakdown:

* Amplitude: The maximum displacement of a wave from its equilibrium position. It represents the "height" or "strength" of the wave.

* Oscillation: The repetitive back-and-forth motion of a wave.

* Magnitude: The size or strength of something.

So, amplitude is the measurement of the *magnitude* of the *oscillation* of a wave.