Frequency (noun)

1. The number of occurrences of a repeated event per unit time.
2. The rate at which something occurs over a particular period of time or in a particular sample.
3. The ratio of the number of times an event occurs to the total number of events.
4. The relative number of times something happens or is present.

Origin:

From middle english frequence, from old french frequence, from latin frequentia ("crowd, assembly"), from frequentem ("crowded, frequent"), from frequentare ("to frequent"), from frequentem ("frequent, crowded").

Examples:

1. The frequency of earthquakes in the region is low.
2. The frequency of his visits has increased.
3. The frequency of the radio station is 97.5.
4. The experiment was conducted at a frequency of 50 Hz.
5. The word "the" has the highest frequency in the text.