**S(t)=A*cos(2*pi*f*t+p)**where:

A = Amplitude (constant)

f= Frequency (constant)

t= Time (changing)

p= Phase

My question is about Phase. Is the phase constant for periodic waves like this Cosine wave? I used *one* value in the equation above & that's what made me think phase is constant. However, when I saw examples of phase spectra of periodic waves I noticed that phase actually changes.

My conclusion, so far, is that "phase" is not constant. Each point on the wave has its own phase, but points at equivalent locations (i.e. one cycle apart) have the same phase. The value 'p' in the equation above is actually the so called 'phase shift' because it shifts the entire waveform forward or backward. Is this accurate? Please correct me.