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From an English test on Facebook:

When you have finished to move the furniture, let me know.


When you will finish moving the furniture, let me know.

I think the correct one is the former, but (if so) why exactly is the second one wrong?

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up vote 4 down vote accepted

When you have finished to move the furniture, let me know

This is simply wrong. English speakers would not use the infinitive here, but the gerund form of the verb: "When you have finished moving the furniture, let me know."

When you will finish moving the furniture, let me know

This has a strange sound to it. I suppose you could use a somewhat less strange-sounding version of this, perhaps "Let me know when you will finish moving the furniture," implying that you expect the addressee to complete that action and are wondering about his intentions in that regard. It also implies that you are interested in the time the process will get under way. It is not grammatically incorrect to reverse the order of the request, as you have in your example, but it just sounds odd.

In short, both constructions sound as if they originate from a non-native speaker.

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In the explanation of #1, the point is not the infinitive versus the present perfect, but the infinitive versus the gerund. – Tsuyoshi Ito Dec 4 '10 at 16:13
@Tsuyoshi Ito: Yep, my bad. I was thinking of "have finished" instead of "moving"; act in haste, repent at leisure. Editing to adjust. Thanks. – Robusto Dec 4 '10 at 16:35
I would say "Let me know when you finish moving the furniture," instead of "Let me know when you will finish moving the furniture." Unless of course, I actually wanted to know when the person planned to finish moving the furniture. I don't think that that's what this is about though. – aaronasterling Dec 5 '10 at 0:14

In normal English (i.e. aside from legalese) we hardly ever use an explicitly future tense ("will", "shall", "will have") with a subordinating conjunction such as "if", "when", or "after" (but not, I think, "although");

There are some apparent exceptions with "if", such as

"If he will go, I'll go with him",

which has a slightly different meaning from

"If he goes, I'll go with him"

but I actually think that this is only formally a future, and really uses the auxiliary in an older sense, meaning "If he is willing to go", so it is actually present tense. (For me it implies that he may be unwilling to go, and the statement is an offer, whereas the second is simply a neutral statement of intent.)

But I can't think of an exception with "when".

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Thanks that's really useful insight! – Uberto Dec 5 '10 at 10:21
Just to add more perspective, the sentence, When you will finish moving the furniture, let me know, would be fine in, say, French or Spanish, where the future must be made explicit when referred to. This is not the case in English, thus the correct form would be: When you finish moving the furniture, let me know. – Jimi Oke Dec 14 '10 at 19:32
@JimiOke, in Spanish "when you finish" with a future sense of "finish" would be "cuando acabes", using the present subjunctive, not the future. So your statement about Spanish isn't really very precise. – dainichi May 24 '13 at 2:33
@dainichi, I'm sorry, I don't even know why I included "Spanish" in my comment. French I studied, but Spanish I did not! Apologies for making unfounded claims! – Jimi Oke May 25 '13 at 12:23

protected by Will Hunting Nov 14 '12 at 12:22

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