Merriam-Webster Collegiate Dictionary - rhythm

 noun  Etymology: Middle French & Latin; Middle French ~e, from Latin ~us, from Greek ~os, probably from rhein to flow — more at stream  Date: 1560  1.  a. an ordered recurrent alternation of strong and weak elements in the flow of sound and silence in speech  b. a particular example or form of ~ iambic ~  2.  a. the aspect of music comprising all the elements (as accent, meter, and tempo) that relate to forward movement  b. a characteristic ~ic pattern rumba ~; also meter I,2  c. the group of instruments in a band supplying the ~ — called also ~ section  3.  a. movement, fluctuation, or variation marked by the regular recurrence or natural flow of related elements the ~s of country life  b. the repetition in a literary work of phrase, incident, character type, or symbol  4. a regularly recurrent quantitative change in a variable biological process a circadian ~ — compare bio~  5. the effect created by the elements in a play, movie, or novel that relate to the temporal development of the action  6. ~ method