2

I've read the question about Future Simple and Future Perfect, but I still can't understand the exact usage of these two tenses.
Is there any diffrence between the following?

I will do my homework by 6 p.m.
I will have done my homework by 6 p.m.

I will do my homework after school
I will have done my homework after school

Also, I've checked the word 'by' in Oxford dictionary and there're some confusing examples:

By the time (that) this letter reaches you I will have left the country.

Can I use 'By the time (that) this letter reaches you I will leave the country' instead?

2

The difference is in the reference point of time where the speaker perceives him/herself to be.

I will do my homework by 6 p.m.

The time is sometime before 6pm, and the speaker is simply asserting an intention to do the homework before the stated time.

I will have done my homework by 6 p.m.

The time when this sentence is spoken is the same as before, but the speaker is moving the reference point to some time in the future after 6pm. Effectively s/he is saying that "When we next speak (at sometime after 6pm) to see what my homework status is, I will be able to say that I have done my homework".

The future perfect tense is useful when discussing something else that is to happen. For example

"Let's go to the cinema tonight. The movie starts at 7pm and it takes half an hour to get there. Can you come?"

"I think so. I will have done my homework by 6pm, which gives us half an hour to eat something before we need to leave. So yes, let's go."

1

With future perfect (F2) you jump to a point in the future, turn round and say some action is finished then. Actually a complicated thing and cumbersome and in most cases you can express the same idea much simpler without using F2. This tense existed in Latin and it was imitated by writers.

I don't believe that it is used very often in spoken langage with reference to the future. But it is used in spoken language for assumptions with high probability when speaking of an event in the past:

  • The burglar will have entered the house at night.

The funny thing is the grammatical tense is F2, but we speak of an event in the past.

A bit deceiving is the fact that grammars explain F2 as a special future tense without mentioning that it is relatively seldom used for speaking of the future.

The second use of F2 for speaking about something in the past is seldom mentioned in grammars.

0

My assertion is, the two sentences converge in terms of meaning. The first sentence means he/she will have cleared the homework, same to the second sentence. It is pretty difficult telling the difference between these tenses thus so much confusions.

0

In my understanding, the usage of Future Simple Tense and Future Perfect Tense are almost the same. However, if you would like to convey a special meaning about the precedence of one action against the other you can differentiate it with the use of Future Perfect Tense:

S.1. When my mother comes back home from her office, I will have left for the cinema. This sentence implies that when my mother comes back home, I will not be there at home. It is looking into the past from a point of time in the future and saying what that time would be like (the house without me).

S.2. When my mother comes back home from her office, I will leave for the cinema. This sentence indicates that when my mother comes back home, I will be at home. I will leave after my mother comes back or as soon as my mother comes back home. It is looking into the future conveying that I will be able to see my mother at least for a fraction of a moment before I leave for the cinema.

S.3. I will have done my homework before school.

S.4. I will have done my homework after school.

Here S.4. cannot be accepted as correct English. It will be more meaningful to say "I will do my homework after school. It is because the perfect tense needs an endpoint of time to show the completion of the action like the adverb of time 'before' in S.3. Whereas, in S.4. the adverb of time is 'after' which implies a starting point of a time with no clue to endpoint.

Compare the following two sentences:

S.5. When he reached the cinema, the show had started.

S.6. When he reached the cinema, the show started.

Here in S.6. the show started after/as soon as he reached the cinema. Whereas, in S.5. the show started before he reached the cinema. Now you can understand that if you want to specifically state the precedence or the completion of the action before a point of time of an action you can use the Perfect Tense; if not, use the Simple Tense. We can also note that in S.5. the show had run at least for a fraction of a second before you reached; and S.6. implies that there is a wait time of at least a fraction of a second for the show to begin.

S.3. I will have done my homework before school.

S.7. I will do my homework before school.

I do not see much difference in the meaning of S.3. and S.7. Both the sentences mean that the homework will be done before school. This is the general sense people make when they use either sentence. Probably, this is why the Simple Future is more commonly used in place of Future Perfect even by the native speakers.

S.8. If you drive at this speed, the show will have started by the time you reach the theatre. S.9. If you drive at this speed, the show will start by the time you reach the theatre. Here we can see clearly that S. 8. can be written as S.9. and 9 as 8 without any change in the meaning. Although we feel the necessity of differentiating Future Perfect from Future Simple in S.1. and S.2., the meaning can be clearly expressed with Future Simple Tense. S.1. When my mother comes back home from her office, I will have left for the cinema. This can be written as "Before my mother comes back home from her office, I will leave for the cinema". S.2. When my mother comes back home from her office, I will leave for the cinema. This can be written as "After/As soon as my mother comes back home from her office, I will leave for the cinema".

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.