Rhythm consists of the repetition of a measure (the length of a cycle) at a certain frequency (rate of events per unit of time). There are two classes of rhythmic behavior: periodic and aperiodic. A periodic rhythm would be day fading into night, and night brightening into day; an aperiodic rhythm might be the flow of information from an internet stream. Additionally, rhythms may be nested within each other; for example, the broadcast of the local news at set intervals throughout the day, throughout the week, is an example of a nested rhythm.