A discrete signal is a signal that has been sampled from a continuous signal.
Unlike a continuous signal, a discrete signal is not a continuous function but a sequence.
Each value in the sequence is called a sample.
Since a discrete signal is a sequence of samples, the sampling rate must be stored seperately (implicitly or explicitly) since the sampling rate cannot be extraced from the samples.
This ambiguity is the basis for the establishment of the Shannon-Nyquist sampling theorem.
This ambiguity also leads to problems in digital frequency.
