Frequency refers to how often an event or occurrence happens. In probability, frequency describes the number of times an event or outcome occurs in repeated trials or experiments. It is often used to estimate the probability of that event. For example, rolling a die $1000$ times and recording the frequencies of the different outcomes. In statistics, frequency describes how many times a specific value, range of values, or category appears in a data set, which helps to summarize and analyze the data distribution. Consider the following data set containing the ages of ten junior high school students.

Ages of Ten Junior High School Students
$12$	$13$	$13$	$14$	$13$
$14$	$12$	$15$	$12$	$14$

In this data set, the age $13$ appears $3$ times, so its frequency is $3.$ This type of frequency is also called the absolute frequency.