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I read (or do I say "have read"?) many rules for when to use the present perfect. I found them complex and hard to understand (or do I say "have found"?). I am finding it hard to apply these rules in real sentences.

Is there a simple and clear way to explain the difference between past simple and present perfect? If there is a simple explanation, please tell it! If there is no simple explanation, please tell why it is so complicated. Maybe if I knew why there is no simple explanation, that would help me understand what work I need to do in order to learn the difference.

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    This question appears to be off-topic because one could write a book on "the real difference" between the two tenses (or aspects). – Damkerng T. Dec 13 '14 at 19:43
  • Technically, it's a yes-or-no question, so I'll answer it that way. I think it might be helpful to have a short explanation of why it can't be done. – Ben Kovitz Dec 13 '14 at 23:05
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    One main difference is that present-perfect is often used when the speaker wants to indicate or stress that a situation that has started in the past is still important now in the present time or the present conversation. :) – F.E. Dec 13 '14 at 23:16
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    There are lots of sentences where you can use either one with the same meaning. There are also lots of sentences where using the wrong one will sound funny. And finally, there are lots of sentences where you can use either one, but the meaning or the emphasis of the sentence will be different. – Peter Shor Dec 14 '14 at 1:23
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    Though my opinion still stands (that the topic is complicated enough to write a book on that; I wish I had more time to write a longer explanation, which is now unnecessary, why I think a short, simple discussion is not going to be the real answer for learners; I'm glad that Ben Kovitz's discussed that, nicely), I decide to vote to reopen this question, seeing that it's likely that we're going to have more good discussions out of this thread. – Damkerng T. Dec 14 '14 at 11:30
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Short answer: Yes

The difference is that the past tense means the action happened at some specific time in the past, and the present perfect means the action happened at an unstated time during a certain time interval that started in the past and continued to the present—maybe more than once during that time interval, depending on what you're talking about.

This action occupied the entire time interval from 1997 until now, and will probably continue:

Brenda has worked at Merriam-Webster since 1997.

This action occurred sometime during the speaker's life so far, perhaps many years ago, perhaps recently, perhaps more than once:

I have seen war.

This action occurred at the very end of the time interval (the time interval is that of the whole race):

Jones has won the race!

Long answer: No

The reason this topic is hopelessly complicated is because reality provides an infinity of different situations, and what time interval is reasonable to talk about varies for each situation.

For example, the time interval for the following question starts at roughly 11:00 a.m. this morning:

Have you eaten lunch?

The question literally means, "During the part that has elapsed so far today of the daily time interval when people normally eat lunch, did you eat lunch?" If you already ate lunch, then you probably don't want to go to lunch now; if you did not already eat lunch, then you might be interested in going to lunch with the speaker now. A person wouldn't ask that question after the middle of the afternoon, because that would be too much later than the normal time to eat lunch. The question leads you to think of the time period for lunch as a sort of window of opportunity that is still open, and asks whether that opportunity has already been exercised.

There's another source of endless complexity: the fact that you are referring to a time interval influences the way a listener understands the verb after have as well as the other words in the sentence.

For example, this sentence means that Chris performed the duty of phone-answerer last week, and answered the phone many times:

During the past week, Chris has answered the phone.

Using the perfect tense suggests that you might mean that the action fills the entire time interval, so the above sentence leads a listener to understand answering as performing a week-long duty to answer the phone whenever it rings. (This would probably be at a business.) Also, it would be strange to speak of a single instance of answering the phone in the present perfect if it happened at some unspecified time during the past week. If Chris answered the phone four days ago, the phone call is surely over by now.

The next sentence probably means that Chris answered the phone once. But it could also mean the same as the previous sentence:

During the past week, Chris answered the phone.

The reason it could mean the same as the previous sentence is the time interval is explicitly spelled out, and answering can still be understood as performing phone-answering duty, regardless of the tense. The past tense doesn't suggest that the action filled the time interval, so it doesn't suggest the “week-long duty” interpretation as strongly as the present perfect. But the past tense doesn't contradict that interpretation, either.

I spoke.

I have spoken.

The first of the above sentences just means that you said something. The second one means that you have said everything you have to say, and probably that you don't want to listen to or address any objections. Because the present perfect suggests a time interval that ends at the present moment, it can suggest that an action filling that time interval is now complete and will not continue. Obviously, though, that's not the intended meaning of the earlier example of someone working at Merriam-Webster since 1997.

Here's an example that follows the basic principle plainly, but is still subtle:

I wrote two novels in 2009.

I have written two novels. [The time interval is the speaker's whole life so far.]

I have written two novels in 2009. [Ungrammatical, because 2009 is over. But this would be grammatical if said during 2009.]

I have written two novels this year. [This is OK, because this year is still present.]

Yet another use of the present perfect is to establish the time frame for a news story. “Until now, most efforts to capture carbon have been expensive, in dollars and in energy.” The past tense (“were expensive”) would mean the same thing, but the present perfect suggests that the rest of the story will describe how that technology is now changing. It leads the reader to expect that the time period covered by the story will be very broad, on the order of years. Beginning a news story in the past tense suggests a very short time frame.

You just have to learn through experience to understand why people sometimes want to refer to a time interval rather than just the specific event. And you learn to infer what that time interval is, since it's usually implicit. Eventually it becomes effortless, but no simple rule could ever cover all situations.

  • Ben sir, in the above explanation, looking at your sentence of 'During the past week Chris has answered the phone', you say here we are talking about the week the ended and it doesn't extend upto the present. Then, what I don't understand is how we can use present perfect with "During the past week Chris has answered the phone" when we mean the week that ended as we have set a timeframe and hence can't use the present perfect. Please clear the doubt sir. Thank you. – Policewala May 8 '16 at 3:46
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    @Policewala Last week designates a seven-day timeframe which ended in the past, but the past week and the last week designate a seven-day timeframe which extends right up to the present. – StoneyB on hiatus May 17 '16 at 21:44
  • But StoneyB, in his phrase For example, this sentence means that Chris performed the duty of phone-answerer last week, and answered the phone many times:" above does last week here mean the week that ended or the week coninues upto now? Thiconfuses me. Please help. – Policewala May 18 '16 at 5:38
  • @Policewala Excellent question! Now I see that I wrote that part of the answer without awareness of how much it depended on the reader's understanding subtle Engilsh idioms about time. For simplicity, imagine that the sentence "During the past week, Chris has answered the phone" is said on Monday, with the understanding that "the past week" and "last week" refer to the same seven-day period, ending in the present—even though, as StoneyB said, "the past week" and "last week" don't always refer to the same seven days. I'll try to think of a way to revise my wording in the answer. :) – Ben Kovitz May 18 '16 at 10:11
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    @AlanEvangelista Ah, now I see. I think the subordinate clause, starting with "that", caused confusion. The time interval extends continuously from the past to the present. The action or actions need not extend to the present. The action or actions are "inside" the time interval, perhaps filling it, perhaps scattered within it, perhaps overlapping with it, perhaps occurring only at the very end. (When I wrote that sentence, I was wondering if it might induce this misunderstanding. I'll think about how to make it clearer.) – Ben Kovitz Oct 6 at 23:11
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Focus on your purpose.

Use simple past to:

  • describe a past action that ended in the past. (I read an article last week.)

  • describe an event at a specific time. (I tried the quiche at Mary's party.)

Use present perfect to:

  • describe events that started in the past but continue at least into the present. (I have found it hard to understand. -- i.e. I still do)

  • describe an action that has occurred in the past and will occur again (I have gone running every day this week. -- I will again)

  • describe an experience at an unspecified time in the past. (I have tried the quiche. It was great.)

  • describe a recently completed event in combination with the word "just." (I have just tried the quiche and I am full.)

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Yes, there is a simple differentiation.

“I have done” describes me (by saying that I have the property of {having done {the thing in question} }).

“I did” makes a historical statement about the past.

(Source: a book I read once; no idea which one.)

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