The motion made by the projection of an object in uniform circular motion on the diameter is simple harmonic motion:

The displacement of simple harmonic vibration x = rcos (ω t+φ);

The velocity of simple harmonic vibration v =-ω rsin (ω t+φ);

The acceleration of simple harmonic vibration is a =-ω 2COS (ω t+φ), and the above three equations are all simple harmonic vibration equations.

Let's see if it's displacement or speed.