Definition: off the site
http://www.statistics.com/index.php?page=glossary&term_id=278
A relative frequency distribution is a tabular summary of a set of data showing the relative frequency of items in each of several non-overlapping classes. The relative frequency is the fraction or proportion of the total number of items belonging to a class.

http://wiki.answers.com/Q/Relative_frequency_formula
Probability of event = relative frequency = f/n
f is the frequency of the event occurrence in a sample of n observances.

Definition: in my own words
the absolute frequency is the number of times the event occurred taken as an estimate of probability.