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I have read this question: “I like to do (be) something” vs “I like doing (being) something” and I get (although the answer could not be applied to my example) that using "to do" means in general I like to do it. While "doing", means I'm doing it at the moment or soon will be.

I found the following example in a grammar book:

Exercise means doing something with the body.

Shouldn't it be "Exercising means doing..." or "Exercise means to do..." or maybe "To exercise means doing ..."

-I don't get why exercise is used as a noun here.

-I don't get why doing is used instead of to do and if they are interchangeable (without context)

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up vote 1 down vote accepted

Firstly: exercise is a noun

Exercise noun -

  1. bodily or mental exertion, especially for the sake of training or improvement of health: Walking is good exercise.
  2. something done or performed as a means of practice or training: exercises for the piano.


Exercise means doing something with the body.

Doing in this sense is a gerund. This means that doing is behaving as a verb within a noun phrase. So doing something with the body is effectively a noun that includes an action.

The sentence itself is acting as a definition for exercise, which is why the part after means is a noun.

To further clarify why using to to do is not natural, if you look at the accepted answer to the question you link to, then you can read this:

The infinitival is more associated with change, the gerund-participle with actuality.

Since your sentence is a definition, it is actuality, therefore we use the gerund doing not the infinitive to do.

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I think doing might be a gerund – simchona Aug 18 '11 at 8:18
I think you're right. – Matt E. Эллен Aug 18 '11 at 8:24
ok, but why use "doing" here and not "to do" instead? – user12049 Aug 18 '11 at 8:25
@repecmps Because the infinitive of the verb (i.e. to do) doesn't fit into the noun phrase. You need to use a gerund for that. – Matt E. Эллен Aug 18 '11 at 8:33
@repecmps: It's a parallel: the sentence says "noun means noun". "Doing" can be a noun, but 'to do' is a verb. – simchona Aug 18 '11 at 8:38

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