rhythm
noun.
the basic rhythmic unit in a piece of music
the piece has a fast rhythm|the conductor set the beat
noun.
recurring at regular intervals
noun.
an interval during which a recurring sequence of events occurs
the never-ending cycle of the seasons
Synonym: cycle, round
noun.
the arrangement of spoken words alternating stressed and unstressed elements
the rhythm of Frost's poetry
Synonym: speech rhythm
noun.
natural family planning in which ovulation is assumed to occur 14 days before the onset of a period (the fertile period would be assumed to extend from day 10 through day 18 of her cycle)