rheo-

Proto-Indo-European root meaning "to flow."

It forms all or part of: amenorrhea; catarrh; diarrhea; gonorrhea; hemorrhoids; maelstrom; rheo-; rheology; rheostat; rheum; rheumatic; rheumatism; rheumatoid; rhinorrhea; rhythm; seborrhea; stream.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit sravati "flows," srotah "stream;" Avestan thraotah- "stream, river," Old Persian rauta "river;" Greek rhein "to flow," rheos "a flowing, stream," rhythmos "rhythm," rhytos "fluid, liquid;" Old Irish sruaim, Irish sruth "stream, river;" Welsh ffrwd "stream;" Old Norse straumr, Old English stream; Lettish strauma "stream, river;" Lithuanian sravėti "to trickle, ooze;" Old Church Slavonic struja "river," o-strovu "island," literally "that which is surrounded by a river;" Polish strumień "brook."

"study of the deformation of the flow of matter," 1929, from French rhéologie; see rheo- "current of a stream" + -logy "study of." Related: Rheologist; rheological.

1843, "instrument for regulating or adjusting the resistance in a circuit," coined by English inventor Charles Wheatstone from Greek rheos "a flowing, stream" (see rheo-) + -stat "regulating device." Related: Rheostatic.