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.

---

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.

---

cardio- British  

combining form

1. heart

   cardiogram

---

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

You might be forgiven for mistaking this as a nightclub but the 50 people - mostly women - are here for an hour of cardio and strengthening.

From BBC • Mar. 21, 2026

This Shakespearean traveling show, now at the Montalbán Theatre in Hollywood through Saturday, is a daredevil feat of memory, theatrical bravado and cardio fitness.

From Los Angeles Times • Jan. 25, 2026

I do cardio five to six days a week, and strength training three times a week.

From The Wall Street Journal • Jan. 5, 2026

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

From MarketWatch • Jan. 2, 2026

Around the room there were more girls now, mostly on the cardio machines, headphones on, pumping away on the treadmills and ellipticals, but some were lifting weights just like I was.

From "Tradition" by Brendan Kiely