a combining form meaning “heart,” used in the formation of compound words: cardiogram.
Also especially before a vowel, cardi-.
Origin of cardio-
< Greek kardio-, combining form of kardía
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
before a vowel cardi-
Word Origin for cardio-
from Greek kardia heart
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
before vowels cardi-, word-forming element meaning "pertaining to the heart," from Latinized form of Greek kardia "heart" (see heart (n.)).
Online Etymology Dictionary, © 2010 Douglas Harper
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.