Graphs of the way in which voltages and currents change repetitiously in circuits are called waveforms. The waveforms have an identifiable shape which is called a waveshape. The time parameter of waveforms relates to the cyclic nature of the change that is taking place. Identifying individual cycles is a prerequisite to determining the time or period of a waveform. Related to the time or period parameter is the frequency of the waveform.
Frequency defines how frequently or how often the waveform occurs in one second of time.
The time and frequency parameters are indirectly related. If one cycle takes a long time to occur, there can be fewer cycles in one second of time and vice versa. The amplitude terminology used to describe AC voltages and currents can be somewhat complicated. With DC voltages and currents that have constant values, the terminology is simple. Time is not a consideration.