1.John helps his mother while she cooks.

2.John helps his mother while she is cooking.

3.John helps his mother while she has been cooking.

(A) Are the above sentences correct? I guess first and second sentences may be correct. but I don't know third sentence is correct. and,

(B) I want to know how to use 'while' with tenses.(For an example, when main clause is simple/continuous/perfect/perfect continuous[present,past or future], which tenses must be used with 'while in sub-clause'?)

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    I've never met a girl called John, are you sure it shouldn't be his mother? – Joe Dark Nov 13 '14 at 14:13
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    @JoeDark: Maybe Mary is sick so she cannot help her mother. Her friend John came over to help her mother. Isn't that nice of him? – oerkelens Nov 13 '14 at 14:14
  • @oerkelens then it would be John helps Mary's mother while she cooks. etc. – Joe Dark Nov 13 '14 at 14:17
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    @JoeDark: There is no reason at all for that. As long as the context is clear (which it might be - but we only have one sentence here) why would you include extra words? Peter helps Mary's father in the garden. John helps her mother while she's cooking. – oerkelens Nov 13 '14 at 14:21
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    @Joe Dark My apology for the mistake. I edited the question. – mark M Nov 13 '14 at 15:34

Yes, 1 and 2 are both valid and mean the same thing. In this context, "she cooks" and "she is cooking" are both in the present tense, so there's no practical difference.

3 does not make sense because the tense has shifted in a nonsensical way. "John helps", present tense, but "while she has been cooking", past perfect. As the helping presumably must happen at the same time as the cooking, the two ideas should be in the same tense. Either as done in examples 1 and 2, or 3 could be reworded to, "John has been helping her mother as she has been cooking."

This is not to say that it is always wrong to have two different verb tenses in the same sentence. It could make perfect sense if the events happen at different times. To take a simple example, "John IS HELPING her mother today and he WILL HELP her again tomorrow."

  • It seems to be "present perfect continuous", not part perfect in sentence 3. – CowperKettle Nov 13 '14 at 15:39
  • I wonder would it be okay to say "John is helping his mother while she is cooking", synchronizing the tenses to present progressive. – CowperKettle Nov 13 '14 at 15:42
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    @Jay Do you say "John has been helping his mother while she has been cooking" is correct (because the same tenses)? – mark M Nov 13 '14 at 15:54
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    @CopperKettle I'd say yes, no question. – Jay Nov 13 '14 at 21:18
  • @Jay So, Can I say "john has helped his mother while she has cooked"(because the same tenses)? – mark M Nov 14 '14 at 14:25

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