cardio

¹ American  

[kahr-dee-oh] / ˈkɑr di oʊ /

noun

Informal.

1. aerobic exercise that stimulates and strengthens the heart and lungs.

   I mostly use weights, but I always add a little cardio into my routine.

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adjective

Informal.

1. of or relating to aerobic exercise.

   The class begins with a slow and steady warmup, and then it switches to a cardio workout.

2. of or relating to the heart; cardiovascular.

   He's a hugely successful cardio surgeon.

cardio- ² American  

1. a combining form meaning “heart,” used in the formation of compound words.

   cardiogram.

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cardio- British  

combining form

1. heart

   cardiogram

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Usage

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.

Etymology

Origin of cardio¹

First recorded in 1960–65

Origin of cardio-²

< Greek kardio-, combining form of kardía

Example Sentences

Strength training, cardio and yoga are part of our fitness activities every week.

From MarketWatch • Jan. 2, 2026

But El Amin’s personal training program blends it all: Muay Thai kickboxing, strength training, cardio and self-defense moves to get clients strong — in both body and mind.

From Los Angeles Times • Jan. 1, 2026

The company serves the cardiac rhythm management, neuromodulation, and cardio and vascular markets.

From The Wall Street Journal • Dec. 17, 2025

Part of the cardio growth story is the Watchman product, a small implant that closes the left atrial appendage of patients with atrial fibrillation, or AF.

From Barron's • Oct. 30, 2025

“Kev”—he jumped out of the way of some girl who might have been about to sneeze—“remember how we talked about how my cardio program will keep me from getting sick?”

From "Liar, Liar" by Gary Paulsen