• Swimming is good exercise.
  • Swimming is a good exercise.

I checked all the major dictionaries and they say that it is uncountable when it means (physical or mental activity that you do to stay healthy or become stronger)

I have seen the following examples:

  • Swimming is great exercise. (Longman Dictionary)
  • Swimming is great exercise. (Oxford Advanced Learner's Dictionary)
  • Cycling to work is great exercise. (Cambridge Advanced Learner's Dictionary)

None of them have used "a" before exercise because they say that it is uncounted here. They also say that exercise can be a countable noun when it means a set of movements. What I think is that swimming is not a set of movements and therefore 'a' is not placed before exercise.

Do you think that we can use 'a' in the sentence "Swimming is a great exercise"?

  • Yes, you can. Cf. also "swimming and jogging are two good exercises". (count).
    – BillJ
    Feb 25 at 8:17
  • But dictionaries do not agree with you. They say it is countable when it means 'a set of movement' and not when it means physical activity that we do to stay healthy Feb 25 at 8:19
  • "Exercise is good for you" (non-count). Doing at least two exercises every day is good for you" (count).
    – BillJ
    Feb 25 at 8:28
  • When "exercise" means "form of exercise" or "type of exercise " it is countable.
    – Peter
    Feb 25 at 8:31
  • 1
    In "Swimming is a good exercise" it is a count noun. Cf. "Swimming and jogging are two good exercises".
    – BillJ
    Feb 25 at 8:58

You might want to consider the answer to this similar question. It asks whether or not 'exercise' can be a plural - of course, if there is more than one of something then it can be counted.

Like most non-countable nouns, 'exercise' can be broken into countable units. For example, water is generally considered a non-countable noun, but it can be contained in glasses or bottles which can then be counted, so you could reasonably ask a waiter for "two waters".

"Swimming is exercise" is correct because swimming is being equated with exercise as a whole.

"Swimming is an exercise" is also correct because swimming is one of many forms of exercise.

  • Swimming is a type of exercise. It is not an exercise. Neither is horseback riding or tennis playing or cycling.
    – Lambie
    Feb 25 at 19:39
  • I am sorry to say that your explanation is not relevant. Mar 16 at 13:12
  • We very often say - Give me two waters. (meaning two glasses of waters) It does not, however, mean that the same goes to exercise. Dictionaries explicitly say that it is uncountable when it means physical or mental activity that you do to stay health. If you want to prove that "Swimming is a good exercise" grammatical, you have to provide authoritative reference(s). Your comment seems to contract all authoritative sources. Mar 16 at 13:15
  • @ModernEnglish I'm sorry to say that your opinion isn't relevant. Of course you can count exercises the same was as glasses of water. If you went to a gym and your personal trainer said "I want you to do a minimum of 3 exercises", that would mean 3 different forms of exercise.
    – Astralbee
    Mar 16 at 13:47

Swimming is good exercise. [Okay, uncountable, or mass noun that refers to the activity of swimming]

Swimming is a good exercise. [Buzzer].

What swimming exercises [countable] are needed to learn to do the crawl?

  • To do the crawl, one exercise [countable] is to use a kickboard to practice the leg kicking.
  • Another exercise [countable] is to practice the arm movements, without using your legs, in shallow water.

Swimming and jogging are good exercise. [Okay, uncountable, refers to these things as an activity, no plural.] Compare: Playing tennis and golfing are good exercise too.

exercise, uncountable refers to a particular activity or series of movements viewed as a single action.

Exercise is good for you. Work is not always good for you.

Exercises I like to do include deep knee bends and waist stretches.


  • Longman Dictionary
  • Oxford Advanced Learner's Dictionary
  • Cambridge Advanced Learner's Dictionary)

are right, no a before exercise when it refers to a sports' activity such as: cycling, swimming, jogging, surfing, etc.

And Merriam Webster:

b: bodily exertion for the sake of developing and maintaining physical fitness trying to get more exercise [uncountable]

3: something performed or practiced in order to develop, improve, or display a specific capability or skill [countable] arithmetic exercises vocal exercises

Mine: swimming exercises aka drills

The Exercises

  1. Shred Your Legs: Tombstone Drill

  2. Build Your Back and Shoulders: Kickboard Press and Pull

See the others via the link


Merriam Webster


Among Lexico's definitions of "exercise":

1 mass noun Activity requiring physical effort, carried out to sustain or improve health and fitness. ‘exercise improves your heart and lung power’ 2 An activity carried out for a specific purpose.

So, the following sentences are both correct (but with caveats):

  • Swimming is exercise. (We would be more likely to say "swimming is good exercise" or "swimming is a form of exercise".)
  • Swimming is an exercise. (This is not a likely sentence, though.)

However, the second sentence has a different meaning. If you say "swimming is an exercise", you no longer mean that it is an activity requiring physical effort, carried out to improve health. Instead, by using the countable noun "exercise", you are invoking Lexico's second definition. "Swimming is an exercise" simply means "swimming is an activity carried out for a specific purpose" - a completely different meaning.

You could say "swimming and cycling are both (good) exercise" or "swimming and cycling both give us exercise" or "swimming and cycling are both forms of exercise".

But if you say "swimming and cycling are both exercises", the meaning virtually disappears; you are now simply saying they are both activities.

  • swimming is not an an exercise. No native speaker would say that. It is a form of exercise.
    – Lambie
    Feb 25 at 19:45
  • @Lambie There is no fundamental disagreement between us here: I made the same distinction between "exercise" and "an exercise" as you do in your own answer. The phrase "Swimming is an exercise" is grammatically correct but sounds odd out of context. It might work better as part of a longer sentence - perhaps "swimming is an exercise that I enjoy regularly" or "swimming is an exercise that is examined as part of the course". Of course, in these sentences "an exercise" means something like "an activity", whereas "exercise" as a mass noun refers to activity undertaken to maintain fitness.
    – rjpond
    Feb 25 at 21:03
  • It is grammatically correct. It is not a likely sentence on its own, but I am using it to explain the difference between "exercise" and "an exercise". We are not at all likely to say "Swimming is an activity" either. But it is correct and we might say it under certain circumstances. It is more likely we would say "There are various activities/exercises that [something something]. Swimming is one such activity" or "Swimming is an activity/exercise that [something]". The point is, of course, "an exercise" has a different meaning from "exercise"/"form of exercise".
    – rjpond
    Feb 25 at 21:11
  • @Lambie I have edited my answer to reflect the point of agreement between us - which is that it is unlikely to be spoken as a stand-alone sentence. But I don't accept that it is ungrammatical. On that we must agree to differ.
    – rjpond
    Feb 25 at 21:54
  • So, I guess four dictionaries saying so is not good enough for you. This type of question is so frustrating as the head honchos refuse to weigh in and leaners are misled about how people actually speak.....no sport including drinking is a good exercise.
    – Lambie
    Mar 3 at 18:21

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