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Hi, Emotion: smile

In the sentence "You have to do it in an hour" ,what does in mean? After an hour or before an hour has passed?

  • Is it my turn? Do I have to do that now?------ No, you have to do that in an hour (wait an hour before doing that)
  • If you want to break the record, you'll have to do that in an hour (within an hour)


  • So, I'm having trouble with the meaning of in. Maybe it's simple, but I'm confused.

    Thank you in advance.
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You have to do it in an hour
has two meanings. Here are some paraphrases that can be used to disambiguate the two meanings.

1. You can't take more than an hour to do it.

2. You'll have to do it an hour from now.

do it is vague. It can be taken to mean something which takes time to happen; it can be taken to mean something which happens in an instant. That's why both interpretations of in an hour are possible. With events that happen more or less instantaneously, however, the first meaning is not usually assumed by a listerner.

You have to take your medicine in an hour, for example, is not likely to be taken to mean You can't take more than an hour to take your medicine. Likewise, We'll find out the results of the test in an hour is not likely to be interpreted as We won't take more than an hour to find out the results of the test. These two are going to be heard with the meanings You'll have to take your medicine an hour from now and We'll find out the results of the test an hour from now. Therefore, no paraphrase of in an hour is necessary.

Stative predicates cannot be used with in (an hour) at all. They don't even make sense.

*I know the answer in an hour.
*I am an American in an hour.


Note also that context is often a good disambiguator.

-- I'll bet you can walk through the park really fast. Can you do it in less than 40 minutes?
-- No, but I can do it in an hour.

-- What a nice day! Do you have time to walk through the park now?
-- No, but I can do it in an hour.


CJ
Comments  
Unfortunately, both, or either :-)

Its one of those phrases that's all in the way its said. As you show in your question, it can mean either 'wait an hour before doing that' or 'do that within an hour'. I tend to think that using 'in' for 'within' is not necessarily good english, but it used a lot.

I know that's not much help, sorry! :-)
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 CalifJim's reply was promoted to an answer.
Thak you so much! English is such a strange language... ;-)