Rhythm (Greek ῥυθμός = 'flow', or in Modern Greek, 'style') is the variation of the length and accentuation of a series of sounds or other events. "Rhythm involves patterns of duration that are phenomenally present in the music" with duration perceived by interonset interval (London 2004, p.4). When governed by rule, it is called meter. It is inherent in any time-dependent medium, but it is most associated with music, dance, and the majority of poetry.