NOUN: 1. Movement or variation characterized by the regular recurrence or alternation of different quantities or conditions: the rhythm of the tides. 2. The patterned, recurring alternations of contrasting elements of sound or speech. 3. Music a. The pattern of musical movement through time. b. A specific kind of such a pattern, formed by a series of notes differing in duration and stress: a waltz rhythm. c. A group of instruments supplying the rhythm in a band. 4a. The pattern or flow of sound created by the arrangement of stressed and unstressed syllables in accentual verse or of long and short syllables in quantitative verse. b. The similar but less formal sequence of sounds in prose. c. A specific kind of metrical pattern or flow: iambic rhythm. 5a. The sense of temporal development created in a work of literature or a film by the arrangement of formal elements such as the length of scenes, the nature and amount of dialogue, or the repetition of motifs. b. A regular or harmonious pattern created by lines, forms, and colors in painting, sculpture, and other visual arts. 6. The pattern of development produced in a literary or dramatic work by repetition of elements such as words, phrases, incidents, themes, images, and symbols. 7. Procedure or routine characterized by regularly recurring elements, activities, or factors: the rhythm of civilization; the rhythm of the lengthy negotiations.
ETYMOLOGY: Latin rhythmus, from Greek rhuthmos. See sreu- in Appendix I.
Etymology of rhythm:
DEFINITION: To flow.
Suffixed o-grade form *srou-mo-. a. stream, from Old English stram, stream;
b. maelstrom, from Middle Dutch stroom, stream. Both a and b from Germanic *straumaz, stream.
2. Basic form *sreu-. a. rheo-, –rrhea; catarrh, diarrhea, hemorrhoid, rhyolite, from Greek rhein, to flow, with o-grade rhoos, flowing, a flowing;
b. suffixed form *sreu-m. rheum, from Greek rheuma, stream, humor of the body.
3. Suffixed zero-grade form *sru-dhmo-. rhythm, from Greek rhuthmos, measure, recurring motion, rhythm.
4. Suffixed zero-grade form *sru-to-. rhyton, from Greek rhutos, fluid, liquid. 5. Perhaps zero-grade extended form *srug-. sastruga, from Russian struga, deep place. (Pokorny sreu- 1003.)
From the Math department at the University of Glasgow:
What is a wave?
A wave is a pulse of energy. Waves carry energy away from a central transmitter. Mechanical waves, such as sound waves, need some medium of transmission. Electromagnetic waves, for example radio waves, can carry energy through a vacuum. If a wave is travelling through a medium, the particles of the medium do not move along with it. They vibrate about their equilibrium position, and the energy is transmitted through the interaction of neighbouring particles.