Rhythm (from Greek ῥυθμός, rhythmos, "any regular recurring motion, symmetry") generally means a "movement marked by the regulated succession of strong and weak elements, or of opposite or different conditions". This general meaning of regular recurrence or pattern in time can apply to a wide variety of cyclical natural phenomena having a periodicity or frequency of anything from microseconds to several seconds (as with the riff in a rock music song); to several minutes or hours, or, at the most extreme, even over many years.
Rhythm is related to and distinguished from pulse, meter, and beats:
Rhythm may be defined as the way in which one or more unaccented beats are grouped in relation to an accented one. ... A rhythmic group can be apprehended only when its elements are distinguished from one another, rhythm...always involves an interrelationship between a single, accented (strong) beat and either one or two unaccented (weak) beats.
In the performance arts, rhythm is the timing of events on a human scale; of musical sounds and silences that occur over time, of the steps of a dance, or the meter of spoken language and poetry. In some performing arts, such as hip hop music, the rhythmic delivery of the lyrics is one of the most important elements of the style. Rhythm may also refer to visual presentation, as "timed movement through space" and a common language of pattern unites rhythm with geometry. For example, architects often speak of the rhythm of a building, referring to patterns in the spacing of windows, columns, and other elements of the façade. In recent years, rhythm and meter have become an important area of research among music scholars. Recent work in these areas includes books by Maury Yeston, Fred Lerdahl and Ray Jackendoff, Jonathan Kramer, Christopher Hasty, Godfried Toussaint, William Rothstein, Joel Lester, and Guerino Mazzola.