Save This Word!

a combining form meaning “flow,” “current,” “stream,” used in the formation of compound words: rheoscope.



They're everywhere you turn, but can you identify the 10 types of nouns easily? This quiz will test your mettle against singular, plural, concrete, abstract, common, proper, collective, compound, countable, and uncountable nouns!
Question 1 of 7
Shoelaces, rainbow, toothpaste, and haircuts are all what type of noun?

Meet Grammar Coach

Write or paste your essay, email, or story into Grammar Coach and get grammar helpImprove Your Writing

Meet Grammar Coach

Improve Your Writing
Write or paste your essay, email, or story into Grammar Coach and get grammar help
Compare -rrhea.

Origin of rheo-

Combining form representing Greek rhéosstream, something flowing
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2021


What does rheo- mean?

Rheo- is a combining form used like a prefix meaning “flow,” “current,” or “stream.” It is often used in scientific terms, especially those referring to electrical currents or the flow of fluids in the body.

Rheo- comes from the Greek rhéos, meaning “stream.”

Rheo- is closely related to another combining form, -rrhea, meaning “flow” or “discharge,” which is connected to—you guessed it—the word diarrhea.

Want to know more? Read our Words That Use -rrhea article.

Examples of rheo-

A scientific term that features the combining form rheo- is rheometer, an instrument used for measuring the flow of fluids, especially blood.

The meaning rheometer becomes clearer when you break it down: rheo- means “flow.” The combining form meter means “measure.” So, a rheometer literally translates to “flow measurer.”

What are some words that use the combining form rheo-?

What are some other forms that rheo- may be commonly confused with?

Break it down!

Some fish and amphibians have special, sensory-related organs, rheoreceptors, that help them navigate their environments. Based on the meaning of rheo-, what do rheoreceptors pick up on (are stimulated by)?

British Dictionary definitions for rheo-


combining form

indicating stream, flow, or currentrheometer; rheoscope

Word Origin for rheo-

from Greek rheos stream, anything flowing, from rhein to flow
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medical definitions for rheo-



Current; flow:rheotaxis.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.