As a sinoidal signal in the time domain is defined as
s(time)=amplitude * sin(2Pi*frequency * time + phase)
the phase describes an 'offset' of the signal along the time axis and defines the 'zero crossing' of the signal. An sinoid signal is periodic, therefore usually only phase values from +/-180deg are used.
a picture? should/can we type TeX? is this supported by our wiki setup?