Waveform: A shape formed by plotting instantaneous values of voltage or current as ordinate (y-axis) against time as abscissa(x-axis) is called waveform. Instantaneous Value: The value of alternating quantity at any instant is called instantaneous value.E.g., in above graph v=0 at t=0. Cycle: One complete set of positive and negative values of an alternating quantity. — 1 cycle = 360 ° or 2 Π Cycle is shown as below. Alternation: Half cycle is called one alternation. 1 alternation =180 ° or Π . Alternation is shown as below. Time Period: Time required to complete one cycle is called time period.It is represented by T. Frequency: The literal meaning of frequency is repetition.In alternating quantity terminology it is defined as " Number of times alternating voltage or current cycles are formed on graph in one second is called frequency." The unit of frequency is cy