Rhythm (from Greek ῥυθμός, rhythmos, "any regular recurring motion, symmetry" (Liddell and Scott 1996)) generally means a "movement marked by the regulated succession of strong and weak elements, or of opposite or different conditions" (Anon. 1971, 2537). 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 millions of years.In the performance arts rhythm is the timing of events on a human scale; of musical sounds and silences, of the steps of a dance, or the meter of spoken language and poetry. Rhythm may also refer to visual presentation, as "timed movement through space" (Jirousek 1995,[page needed]) and a common language of pattern unites rhythm with geometry. 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 (Yeston 1976), Fred Lerdahl and Ray Jackendoff, Jonathan Kramer, Christopher Hasty (Hasty 1997), Godfried Toussaint (Toussaint 2005), William Rothstein, and Joel Lester (Lester 1986).In Thinking and Destiny, Harold W. Percival defined rhythm as the character and meaning of thought expressed through the measure or movement in sound or form, or by written signs or words Percival 1946, 1006.