[ kahr-dee-oh ]
/ ˈkɑr di oʊ /
Save This Word!

noun Informal.

aerobic exercise that stimulates and strengthens the heart and lungs: I mostly use weights, but I always add a little cardio into my routine.

adjective Informal.

of or relating to aerobic exercise: The class begins with a slow and steady warmup, and then it switches to a cardio workout.
of or relating to the heart; cardiovascular: He's a hugely successful cardio surgeon.



Call upon your favorite grammar inspirations to tackle this quiz on the differences and uses of "evoke" and "invoke."
Question 1 of 7
“Evoke” and “invoke” both derive from the same Latin root “vocāre.”

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

Origin of cardio

First recorded in 1960–65

Definition for cardio (2 of 2)


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. 2021


What does cardio- mean?

Cardio- is a combining form used like a prefix meaning “heart.” It is used in many medical and scientific terms.

Cardio- comes from the Greek kardía, meaning “heart.” In fact, the English word heart and the Greek kardía are related. Learn more at our entry for heart.

What are variants of cardio-?

When combined with words or word elements that begin with a vowel, cardio- becomes cardi-, as in cardiectomy.

Examples of cardio- 

You may recognize the combining form cardio- from the word cardiogram, which is a recording of the activity of the heart. A cardiogram is also known as an electrocardiogram (EKG), and is used to diagnose heart conditions.

We now know that cardio- means “heart.” The second part of the word, -gram, refers to “something written, recorded, or drawn.” So, a cardiogram has the literal sense of a “heart recording.”

You probably also recognize the word cardio as its own word, short for cardiovascular exercise, such as running. Cardiovascular means “of, relating to, or affecting the heart and blood vessels,” and combines cardio- and vascular. Cardio gets the heart rate up and the blood moving.

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

Break it down!

Based on the meaning of cardio-, a cardiologist specializes in what part of the body?

How to use cardio in a sentence

British Dictionary definitions for cardio


before a vowel cardi-

combining form


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

Medical definitions for cardio



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