will complete/will have completed

[joham]

Dear David and soup,
Thank you for your kind help.
The greatest difficulty for me is not the future perfect tense but the simple future used with 'by the time...'. Those sentences with the future perfect are relatively easy for me to understand and use.

My questions are:
1. Does 'The mist will clear by mid-morning.' mean 'The mist will begin to clear by mid-morning' or 'The mist will have cleared by mid-morning' or neither? (This sentence is taken from Oxford 6.)

Martin Hewings:
He went completely grey by the time he was 25.
To me this sentence means 'He had gone completely grey by the time he was 25.' Then why not use 'had gone' as grammar books say? What is the difference between these two?

Looking forward to your further kind help. Thank you ever so much.

[Raymott]

The greatest difficulty for me is not the future perfect tense but the simple future used with 'by the time...'. Those sentences with the future perfect are relatively easy for me to understand and use.

Often it doesn't matter which form you use (as in your examples).
But at other times it makes a difference.
"1. He went completely grey by the time he was 25.
2. 'He had gone completely grey by the time he was 25.' "
This example uses the simple past tense, and the past perfect (as opposed to the subject line which refers to the simple future and the future perfect).

However, there is a similarity: the future perfect is used to refer to something which happens in the future before something else which happens in the future.
The past perfect refers to something that happened in the past before something else that happened in the past.

I'll use this example:
1. 'The mist will clear by mid-morning.' (simple future).
2. 'The mist will have cleared by mid-morning' (future perfect).

1. is a simple statement of something which will occur in the future.
But imagine you wanted to play football at 10am tomorrow. 10am tomorrow is the time you are interested in. You want to know: "Will the mist have cleared by 10am", that is, will A have occurred before B?
You can then add another clause:
"Will the mist have cleared before we are due to play football?"

A better example:
3. Will she have had the baby before they move house". (You're referring to 2 things that happen in the future, and you are only interested in whether A happens before B. You are primarily concerned with the time at which they move house. That is the reference time. It implies that they will move house at a certain time whether she's had the baby or not.
4. Will she have the baby before they move house".
This seems to mean the same thing, but the emphasis here is on when she will have the baby. In fact, it could mean that she will put off moving house until after she has the baby.

I'm sure there are better examples in which the distinction makes more of a difference, but I can't think of one just now.

[joham]

Thanks a lot, Raymott. I've got a bit clearer now.

1. He went completely grey by the time he was 25.
2. By the age of 21 he controlled the company.
3. The mist will clear by mid-morning.

All these sentences are taken from Oxford 6th edition. They can all be changed into the perfect tense without changing the meaning very much. Right?

I'm still puzzled why grammar books never mention the use of simple tenses with the 'by the time' phrases and their difference from the perfect tenses.

By the way, how do you native speakers pronounce 'will have been done'?
Is it 'will-a-bin done'?

Thank you all again.

[Raymott]

Thanks a lot, Raymott. I've got a bit clearer now.

1. He went completely grey by the time he was 25.
2. By the age of 21 he controlled the company.
3. The mist will clear by mid-morning.

All these sentences are taken from Oxford 6th edition. They can all be changed into the perfect tense without changing the meaning very much. Right?
Yes, they can be changed into the past or future perfect (when the clause stands alone like this). But not the present perfect. You can't say:
He has gone completely grey by the time he was 25. X (Use simple past or past perfect)

I'm still puzzled why grammar books never mention the use of simple tenses with the 'by the time' phrases and their difference from the perfect tenses.
I find it very hard to find a comprehensive grammar book. Most of them leave off just when they are starting to become useful.

By the way, how do you native speakers pronounce 'will have been done'?
Is it 'will-a-bin done'?
I say "will əv been/bin done"

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