n. 1
Any activity designed to develop or hone a skill or ability.
The teacher told us that the next exercise is to write an essay.
n. 2
Activity intended to improve physical, or sometimes mental, strength and fitness.
I like to do my exercises every morning before breakfast. I do calisthenics for physical exercise, and I do crosswords for mental exercise.
n. 3
Activity intended to improve physical, or sometimes mental, strength and fitness. Such activity of physical nature, for physical fitness (plus also mental benefit).
Swimming is good exercise.
v. 1
To exert for the sake of training or improvement; to practice in order to develop.
to exercise troops or horses; to exercise one's brain with a puzzle

Related words

Word family: exercisewear exercycle exercising
Phrases: exercise bicycle vacuum exercise exercise ball military exercise training exercise exercise bike exercise book exercise in futility

Forms

Plural: exercises → practices, drills, actions, trainings…
Past participle: exercised
e.g. exercised → worked, exerted, pursued, applied…

Choose the right word

Exercise or Exertion?

Exercise, in the ordinary sense, is the easy natural action of any power; exertion is the putting of any power to strain and tax. An exercise-drive for a horse is so much as will develop strength and health and not appreciably weary.

J. C. Fernald, English Synonyms and Antonyms (1914)

Example sentences

action A time will come when you will regret your action.
training Lorenzo never crashed a plane during his training.
practice It takes years of practice to play the piano well.
discipline Discipline is the most important part of success.
exertion After much exertion, he was exhausted.
example For example, he speaks German, French and English.

Popularity over time

Word	1850 → 2019	Trend
exercise		steady
action		falling
training		falling
practice		steady
discipline		steady
exertion		steady

Use in printed books, per decade from 1850 to 2019.

By length

2 letters: do¹
3 letters: use¹, try¹, act¹, ply¹
4 letters: work¹, play¹, task¹
5 letters: train¹, labor², apply², worry², usage², drill¹, exert², wield¹
6 letters: action², labour², lesson², pursue², employ², occupy³, assert², harass², praxis²
7 letters: example³, workout²
8 letters: training², practice², activity⁴, function², distress², drilling², practise², exertion³, accustom³
9 letters: operation⁴, appliance³, preoccupy⁴
10 letters: employment³, discipline³, occupation⁴, practicing³, gymnastics³, practising, recitation⁴
11 letters: performance³, application⁴, utilization⁵, utilisation
12 letters: calisthenics⁴
13 letters: callisthenics

The small number after each word is its number of syllables (labor² = 2 syllables).

In other languages

Français: exercice
Italiano: allenamento
Español: ejercicio
Deutsch: Übung
Català: exercici