The relationship between probability and frequency is that relative frequency serves as an experimental measurement of probability. Over a small number of trials, relative frequency may significantly differ from theoretical probability, but it tends to align more closely with the theoretical value as the number of trials increases. For instance, in a coin toss, the theoretical probability of heads is 0.5, which should reflect in the relative frequency over many tosses. The discussion also raises questions about the term "probability frequency," suggesting it may refer to "relative frequency" or "probability density." Clarification on terminology is needed for a better understanding of these concepts.