状语从句之时间状语从句

Using Adverb Clauses with Time Expressions
Punctuation
When an adverb clause begins the sentence, use a comma to separate the two clauses. Example: As soon as he arrives, we will have some
lunch. When the adverb clause finishes the sentence, there is no need for a comma. Example: He gave me a call when he arrived in town.
Adverb Clauses with Time
When

He was talking on the phone when I arrived.
When she called, he had already eaten lunch.
I washed the dishes when my daughter fell asleep.
We'll go to lunch when you come to visit.
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'When' means 'at that moment, at that time, etc.'. Notice the different tenses used in relationship to the clause beginning with when. It is
important to remember that 'when' takes either the simple past OR the present - the dependent clause changes tense in relation to the
'when' clause.
Before
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We will finish before he arrives.
She (had) left before I telephoned.
'Before' means 'before that moment'. It is important to remember that 'before' takes either the simple past OR the present.
After
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We will finish after he comes.
She ate after I (had) left.
'After' means 'after that moment'. It is important to remember that 'after' takes the present for future events and the past OR past perfect
for past events.
While, as
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She began cooking while I was finishing my homework.
As I was finishing my homework, she began cooking.
'While' and 'as' mean 'during that time'. 'While' and 'as' are both usually used with the past continuous because the meaning of 'during that
time' which indicates an action in progess.

By the time

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By the time he finished, I had cooked dinner.
We will have finished our homework by the time they arrive.
'By the time' expresses the idea that one event has been completed before another. It is important to notice the use of the past perfect for
past events and future perfect for future events in the main clause. This is because of the idea of something happening up to another point
in time.
Until, till
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We waited until he finished his homework.
I'll wait till you finish.
'Until' and 'till' express 'up to that time'. We use either the simple present or simple past with 'until' and 'till'. 'Till' is usually only used in
spoken English.
Since
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I have played tennis since I was a young boy.
They have worked here since 1987.
'Since' means 'from that time'. We use the present perfect (continuous) with 'since'. 'Since' can also be used with a specific point in time.
As soon as
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He will let us know as soon as he decides (or as soon as he has decided).
As soon as I hear from Tom, I will give you a telephone call.
'As soon as' means 'when something happens - immediately afterwards'. 'As soon as' is very similar to 'when' it emphasizes that the event
will occur immediately after the other. We usually use the simple present for future events, although present perfect can also be used.
Whenever, every time
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Whenever he comes, we go to have lunch at 's
We take a hike every time he visits.
'Whenever' and 'every time' mean 'each time something happens'. We use the simple present (or the simple past in the past) because
'whenever' and 'every time' express habitual action.
The first, second, third, fourth etc., next, last time
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The first time I went to New York, I was intimidated by the city.

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I saw Jack the last time I went to San Francisco.
The second time I played tennis, I began to have fun.
The first, second, third, fourth etc., next, last time means 'that specific time'. We can use these forms to be more specific about which time
of a number of times something happened.

After, Before, When
The time expressions after, before and when are used to indicate when something happens in the past, present or future. After,
before and when introduce a full clause and require a subject and verb. Therefore, the time expressions after,
before and when introduce adverb clauses.
Each time expression uses different tenses depending on whether the action occurs in the present, past or future. However, the general rule
is that time expressions take the simple form of a given tense. In in other words, after, before and when are followed by either the
present simple for present and future situations, or the past simple for past events. The following guide provides an explanation past, present and
future use indicating tenses required for both the time clause and the main clause. Examples are provided for each usage to provide context.
After
The action in the main clause occurs after what occurs in the time clause with after. Notice the use of tenses:
Future: What will happen after something occurs.
Time clause: present simple
Main clause: future
Examples:
We'll discuss the plans after he gives the presentation.
Jack is going to propose to Jane after they have dinner on Friday!
Present: What always happens after something else occurs.
Time clause: present simple
Main clause: present simple
Examples:
Alison checks her mail after she gets home.
David plays golf after he mows the lawn on Saturdays.
Past: What happened after something (had) occurred.
Time clause: past simple or past perfect
Main clause: past simple
Examples:
They ordered 100 units after Tom (had) approved the estimate.
Mary purchased a new car after she (had) researched all her options.

Before
The action in the main clause happens before the action described in the time clause with 'before'. Notice the use of tenses:
Future: What will happen before something else occurs in the future.
Time clause: present simple
Main clause: future
Examples:
Before he completes the report, he will check all the facts.
Jennifer will speak with Jack before she makes a decision.
Present: What happens before something else occurs on a regular basis.
Time clause: present simple
Main clause: present simple
Examples:
I take a shower before I go to work.
Doug exercises every evening before he eats dinner.
Past: What (had) happened before something else occurred at a point of time in the past.
Time clause: past simple
Main clause: past simple or past perfect
Examples:
She had already eaten before he arrived for the meeting.
They finished the discussion before he changed his mind.

When
The action in the main clause happens when something else occurs. Notice that 'when' can indicate different times depending on the tenses
used. However, 'when' generally indicates that something happens after, as soon as, upon something else occurring. In other words, it
happens just after something else occurs. Notice the use of tenses:
Future: What happens when something else occurs in the future.

Time clause: present simple
Main clause: future
Examples:
We'll go out to lunch when he comes to visit me. (general time)
Francis will give me a call when he gets the confirmation. (after in a general sense - it could be immediately, or later)
Present: What always happens when something else occurs.
Time clause: present simple
Main clause: present simple
Examples:
We discuss the bookkeeping when she comes every month.
Susan plays golf when he friend Mary is in town.
Past: What happened when something else (had) occurred. The past tense of 'when' can indicate that something happened regularly or one
specific time in the past.
Time clause: past simple
Main clause: past simple
Examples:
She took the train to Pisa when he came to visit her in Italy. (once, or on a regular basis)
They had a great time seeing the sights when they went to New York.

While, As, As So Long As
Expressing What Happens During That Time
While As = During that Time
'While' and 'as' are used to describe actions that occur at the same moment that something is in progress. 'While' and 'as' are sometimes
confused with the preposition 'during'. Both express the same idea, however, the structures are different. 'While' and 'as' are time expressions
and take a subject and verb. 'During' is a preposition and is used with a noun or noun phrase. Take a look at the following examples to note
the difference. Notice how the meaning remains the same in both structures:
Examples - During:
We discussed the situation during lunch. (noun)
They are going to visit the Empire State Building during their visit to New York (noun phrase).
The following sentences can also be expressed using the time expressions 'while' or 'as'. Be sure to take careful note of how the structure
changes.

Examples - When As:
We discussed the situation while we were eating lunch. (full adverb time clause with subject and verb)
They are going to visit the Empire State Building as they visit New York. (full adverb time clause with subject and verb)
Future: Use 'while' or 'as' to state something that occurs at the same moment that something else - the main focus of the sentence -
important will occur.
Time clause: present simple
Main clause: future form
Examples:
We're going to speak about the modifications as you eat lunch.
She'll work out the order details while we discuss what to do next.
Present: Use 'while' or 'as' to express what always happens when something else important takes place. This use of 'while' and 'as' is not
as common as the time expression 'when'. Notice that the preposition 'during' is often used in place of 'while' or 'as' to express the same idea.
Time clause: present simple
Main clause: present simple

Examples:
He usually has lunch while he take a walk around the campus.
Angela often takes notes as the meeting progresses.
Past: 'While' and 'as' are used in the past to express an action that was occurring at the moment when something important happened.
'While' and 'as' are also used to express two actions that were happening at the same moment in the past.
Time clause: past simple OR past continuous
Main clause: past simple OR past continuous
Examples:
Doug was drying the dishes while we were watching TV.
Peter took notes as we discussed the merger.

As Long As So Long As = During an Entire Period of Time
'As long as', and 'so long as' are similar in use to 'while' and 'as'. However, 'as so long as' is used for longer period of times, while 'when'
and 'as' are used for more specific, shorter periods of time. 'As so long as' are also used to stress that something will happen, happens or
happened over the entire period of time in an emphatic manner. Although I have provided examples for the past, present and future, 'as long
as' and 'so long as' are generally used with future forms. Notice the use of tenses:
Future: Use 'so as long as' that something will not happen for the entire period of time expressed by the time clause with 'as so long as'.
Time clause: present simple
Main clause: future form
Examples:
I will never play golf as long as I live.
She will never return so long as she breathes.
Present: Use 'as so long as' to express that something happens or doesn't happen over the entire period of time that another event
occurs.
Time clause: present simple
Main clause: present simple
Examples:

As long as he plays piano, I go for a walk.
She visits with her month, so long as her husband has to take care of business in town.
Past: Use 'as so long as' to describe an action that did or didn't occur over a longer period of time in the past.
Time clause: past simple
Main clause: past simple OR past continuous
Examples:
She didn't get any exercise as long as she was working 60 hours a week.
Peter didn't enjoy his company so long as he was in the house.

Confusing Time Words
When While During For Since Ago Before In At On
Time expressions are crucial for understanding how to conjugate a tense in English. In other words, reading 'next Friday' indicates that I
should use a future tense - either the future simple or the future with going to. Sometimes, it's a little easy to get these time expressionsconfused.
This article focuses on key differences and tense usage between commonly confused time words.
In - During
Sometimes 'in' and 'during' are interchangeable. For example:
I saw him in class.
I saw him during class.
The meaning is similar, but not exactly the same. 'In class' uses the preposition 'in' for location, while 'during' is followed by a noun or noun
phrase to indicate that something occurs during that activity.
There are also a number of situations in which both 'in' and 'during' are both used to indicate that something happens within a particular
period of time.
in my vacation during my vacation
in March during March
I'll be leaving this position during in April.
Jack had a good time in during the class.
In - At - On
'In' and 'at' are sometimes confused with time. 'In' is always used with months and years, 'at' with specific times of the day, and 'on' with
days of the week. Review the specific rules of 'in', 'at' and 'on' for time.
Andrea was born in 1987.
My father went to New York in February.
I'll see you at five o'clock.
They always meet on Mondays.
Before - Ago
'Before' is often used in place of 'ago' to indicate something that happened in the past. This is a mistake. State the period of time followed
by 'ago'.
I saw him three weeks ago.
She visited me two years ago.
I had lunch one hour ago.
'Before' is used to introduce a time clause to indicate that something happened before something else. Time clauses with 'before' use either
the present simple or the past simple tense.

We had eaten before he arrived.
We'll discuss the situation before we begin the meeting.
I always exercise before I eat dinner.
While - During
'While' and 'during' are synonymous but use different grammar structures. Use 'while' with a full clause including subject and verb. 'During'
is used with a noun or noun phrase. Notice the similarity and differences in the following examples:
We discussed economics while we were taking the class.
We discussed economics during the class.
While she was preparing dinner, Alan took care of the children.
Alan took care of the children during the meal preparation.
When - While
Both 'when' and 'while' are used to express that something occurred during another action. Use 'when' to express what interrupted the action,
use 'while' to express the action that was interrupted, or to express something that was happening at the same time something else took
place. These examples should help make this clear.
Interrupted Action
Jason was studying for his test when the telephone rang.
While Jason was studying for his test, the telephone rang.
Jennifer was finishing her homework when she heard the baby cry.
She heard the baby cry while she was finishing her homework.
Concurrent Action
Susan completed her homework while her father was watching TV.
While I was doing the shopping, my wife had her hair done.
For - Since
Both 'for' and 'since' are commonly used with the present perfect and present perfect continuous tenses. Remember that 'for' is used with
the amount of time and 'since' with the starting point in time. Review the use of 'since' and 'for' in more detail.
I have lived in this city since 1998.
I have lived in this city for many years.
Jason has been playing volleyball for two hours.
Jason has been playing volleyball since three o'clock.
'For' can also be used with other tenses to indicate a length of time.
I lived in Italy for ten years.
I'm going to work for twenty years and then retire.