Lecture 25,Conditional Sentence
? 1 Definition
? A conditional sentence (or,conditional” for short) is commonly
composed of two parts,conditional clause + main clause,Despite the
many possible sequences of verb forms in conditionals,the following
four types represent perhaps the commonest and the most useful ones,
? I,If you heat ice,it melts,（真理 General conditionals ）
II,If we catch the 10 o’clock train,we will get there by lunchtime,
（真實假設 Open Present or future conditionals ）
III,If we caught the 10 o’clock train,we would get there by
lunchtime,（虛設假設 Unreal Present or future conditionals ）
IV,If we had caught the 10 o’clock train,we would have got there by
lunchtime,（過去虛設假設 Unreal Past conditionals ）
? 2,Types of Conditional Sentence
? Conditional Type 1,Truth (General conditionals)
? 這是一個基於 真理 （ General truth ） 上的假設，來說及一些 不
變定律 或 習慣性 的情況。
? Basic form, if-clause main clause
present simple present simple
? e.g.,If we eat contaminated food,we become ill,
e.g.,If we don't feel well,we see a doctor,
e.g.,If we boil water to 100℃,it changes into steam,
? Conditional Type 2,Real (Open Present or future conditionals)
? 真實的假設,是我們最常用的一種。就是說及 一些現在發生的
事，可能會造成將來那些結果 。
? Basic form, if-clause main clause
? present tense future tense
? e.g.,If it rains tomorrow morning,we will cancel our picnic,
e.g.,If you are hungry now,I will make you some hot cakes,
e.g.,If you want to read the book,I will lend it to you,
? 這三句例子都十分普通，但其實 real conditionals 可以有幾種改
變，發揮出不同的效果,
? " Will " Replaced by " Can/May " 作為 " 應允 "
? e.g.,You can/may borrow my camera if you want to take some
photographs,
?, Will, Replaced by, May/Might/Could, 作為表示, 可能性,
? e.g.,If the no,3 signal is hoisted tomorrow morning,the ferry
services may/might/could be suspended,
?, Will, Replaced by, Can/Could, 作為表示, 能力所及,
? e.g.,If you try hard,you can/could learn to use the computer well,
? " should " being used in If-clause 以表示 " 較低可能性 "
e.g.,I don't think Winkie is going to the party this evening,but if I
should see her,I will give her this message,
? 注意：當我們在 main clause 用上, should,, 那個, if, 可
以刪除。
? e.g.,Should I see her at the party,I will give her your message,
? Using Present Perfect or Present continuous Tense
in If-clause 以表示不同 時態
? e.g.,If it has stopped raining,we can go out now,
e.g.,If you are having dinner now,I will call again later,
? 任何 " 建議性 " 的意思都可用於 main clause
e.g.,If you don't feel well,you would better see a doctor,
you should stay in bed,
you ought not to be working now,
why don't you take a day off?
would you like me to call the doctor?
? Conditional Type 3,Unreal(Unreal Present or future
conditionals及 Unreal Past conditionals)
? It is possible but very unlikely,that the condition will be fulfilled,
? Basic form, if-clause main clause
? past simple would + infinitive
? e.g.,I am busy now,If I had time,I would certainly help you,
e.g.,I don't have a car,If I had one,I would take you for a ride
round the town,
e.g.,I don't think it will rain tomorrow,If it did （ tomorrow）,we
would stay at home and do some reading instead,
? Unreal Present or future conditionals 的變化,
? Using " Were " instead of " Was " 提供一個 嚴肅的風格 (formal
style)
e.g.,If he was/were here now,he would be very glad to see you,
? Using, If I were you,I would…, 以 表示建議
? e.g.,If I were you,I would be confident in using English,
? Using, Might/Could, in main clause以表示一個 可能性 或 能力
所及
? e.g.,If you asked him,he might help you,
e.g.,If you told me,I could perhaps give you some advise,
? Applying Past continuous Tense in If-clause 表示時間
e.g.,My uncle and aunt are taking me to Ocean Park tomorrow,If I
were not going with them,I would be glad to go with you,
? Applying Continuous Tense in auxiliary verbs （ Would + be +
ing ） 以 表示時間
e.g.,If he was here now,we would be playing TV games,
? Conditional Type 4,Unreal Past conditionals
? It is impossible that the condition will be fulfilled because it refers
to the past,
? Basic form, if-clause main clause
? past perfect would + have + ppt
? e.g.,The whether suddenly turned bad yesterday,If we had gone
out,we would have been caught in the heavy rain,
? Unreal Past 的變化,
? Applying Past Perfect Continuous in the If-clause
? e.g.,The driver was driving too fast,If he had been driving slowly,
he would have been able to stop in time to avoid the accident,
? Replacing,Would + have + ppt, with, Might + have + ppt, 表
示 可能性
? e.g.,If you had come earlier,you might have seen him,
? Other conditional expressions
? unless (= if not)
? Unless we hurry,we'll miss our plane,(= if we don't hurry...)
? otherwise
? You must work hard,Otherwise you'll fail the examination,
You should work hard,Otherwise you'd fail the examination,
We got up early,Otherwise we'd have missed the first ferry to Lantau,
? as/so long as,provided/providing that,on condition that
? You can borrow my camera so/as long as
provided/providing that you handle it carefully,
on condition that
? This should be a positive statement,
? even if/though
? She won't tell us even though she knows the answer,
even if
? and/or (else)
? Take this medicine and you'll be all right tomorrow,
Hurry up or/or else you'll be late,
? (Let's) suppose,supposing,imagine,what if
? (Let's) suppose/Supposing it rained tomorrow,What would we do?
? (Let's) suppose/Supposing it had rained yesterday,What would we have done?
? Imagine you had a lot of money,What would you do with it?
Imagine you had won a lot if money,What would you do with it?
What if she told you the truth? Would you forgive her?
What if she had told you the truth? Would you have forgiven her?
? if it were not/had not been for,but for
? If it were not for her /But for her,I would not go to the party tomorrow,
? If it had not been for her /But for her,I wouldn't have gone to the party last night,
? without
Without his help,we wouldn't have succeeded,(= if it had not been for his help...)
? were to
? Were someone to try to break into the house,the alarm would be activated,(= if
someone tired to break into the house...)
? if so,if not
? Do you want to read this novel? If so (= if you do),you can have it,
If not (= if you do not,i will lend it to Melinda.)
Homework
? Exercise 34A on Pages 588-589
? Exercise 34B on Pages 592-594
? Exercise 34D on Pages 596-597
? Exercise 34E on Pages 597-598
? Exercise 34F on Pages 599-600
? Exercise 34G on Pages 600-601
? Exercise 34H on Pages 601-602
? 预习 第 35讲 （ 603-620页）
? 1 Definition
? A conditional sentence (or,conditional” for short) is commonly
composed of two parts,conditional clause + main clause,Despite the
many possible sequences of verb forms in conditionals,the following
four types represent perhaps the commonest and the most useful ones,
? I,If you heat ice,it melts,（真理 General conditionals ）
II,If we catch the 10 o’clock train,we will get there by lunchtime,
（真實假設 Open Present or future conditionals ）
III,If we caught the 10 o’clock train,we would get there by
lunchtime,（虛設假設 Unreal Present or future conditionals ）
IV,If we had caught the 10 o’clock train,we would have got there by
lunchtime,（過去虛設假設 Unreal Past conditionals ）
? 2,Types of Conditional Sentence
? Conditional Type 1,Truth (General conditionals)
? 這是一個基於 真理 （ General truth ） 上的假設，來說及一些 不
變定律 或 習慣性 的情況。
? Basic form, if-clause main clause
present simple present simple
? e.g.,If we eat contaminated food,we become ill,
e.g.,If we don't feel well,we see a doctor,
e.g.,If we boil water to 100℃,it changes into steam,
? Conditional Type 2,Real (Open Present or future conditionals)
? 真實的假設,是我們最常用的一種。就是說及 一些現在發生的
事，可能會造成將來那些結果 。
? Basic form, if-clause main clause
? present tense future tense
? e.g.,If it rains tomorrow morning,we will cancel our picnic,
e.g.,If you are hungry now,I will make you some hot cakes,
e.g.,If you want to read the book,I will lend it to you,
? 這三句例子都十分普通，但其實 real conditionals 可以有幾種改
變，發揮出不同的效果,
? " Will " Replaced by " Can/May " 作為 " 應允 "
? e.g.,You can/may borrow my camera if you want to take some
photographs,
?, Will, Replaced by, May/Might/Could, 作為表示, 可能性,
? e.g.,If the no,3 signal is hoisted tomorrow morning,the ferry
services may/might/could be suspended,
?, Will, Replaced by, Can/Could, 作為表示, 能力所及,
? e.g.,If you try hard,you can/could learn to use the computer well,
? " should " being used in If-clause 以表示 " 較低可能性 "
e.g.,I don't think Winkie is going to the party this evening,but if I
should see her,I will give her this message,
? 注意：當我們在 main clause 用上, should,, 那個, if, 可
以刪除。
? e.g.,Should I see her at the party,I will give her your message,
? Using Present Perfect or Present continuous Tense
in If-clause 以表示不同 時態
? e.g.,If it has stopped raining,we can go out now,
e.g.,If you are having dinner now,I will call again later,
? 任何 " 建議性 " 的意思都可用於 main clause
e.g.,If you don't feel well,you would better see a doctor,
you should stay in bed,
you ought not to be working now,
why don't you take a day off?
would you like me to call the doctor?
? Conditional Type 3,Unreal(Unreal Present or future
conditionals及 Unreal Past conditionals)
? It is possible but very unlikely,that the condition will be fulfilled,
? Basic form, if-clause main clause
? past simple would + infinitive
? e.g.,I am busy now,If I had time,I would certainly help you,
e.g.,I don't have a car,If I had one,I would take you for a ride
round the town,
e.g.,I don't think it will rain tomorrow,If it did （ tomorrow）,we
would stay at home and do some reading instead,
? Unreal Present or future conditionals 的變化,
? Using " Were " instead of " Was " 提供一個 嚴肅的風格 (formal
style)
e.g.,If he was/were here now,he would be very glad to see you,
? Using, If I were you,I would…, 以 表示建議
? e.g.,If I were you,I would be confident in using English,
? Using, Might/Could, in main clause以表示一個 可能性 或 能力
所及
? e.g.,If you asked him,he might help you,
e.g.,If you told me,I could perhaps give you some advise,
? Applying Past continuous Tense in If-clause 表示時間
e.g.,My uncle and aunt are taking me to Ocean Park tomorrow,If I
were not going with them,I would be glad to go with you,
? Applying Continuous Tense in auxiliary verbs （ Would + be +
ing ） 以 表示時間
e.g.,If he was here now,we would be playing TV games,
? Conditional Type 4,Unreal Past conditionals
? It is impossible that the condition will be fulfilled because it refers
to the past,
? Basic form, if-clause main clause
? past perfect would + have + ppt
? e.g.,The whether suddenly turned bad yesterday,If we had gone
out,we would have been caught in the heavy rain,
? Unreal Past 的變化,
? Applying Past Perfect Continuous in the If-clause
? e.g.,The driver was driving too fast,If he had been driving slowly,
he would have been able to stop in time to avoid the accident,
? Replacing,Would + have + ppt, with, Might + have + ppt, 表
示 可能性
? e.g.,If you had come earlier,you might have seen him,
? Other conditional expressions
? unless (= if not)
? Unless we hurry,we'll miss our plane,(= if we don't hurry...)
? otherwise
? You must work hard,Otherwise you'll fail the examination,
You should work hard,Otherwise you'd fail the examination,
We got up early,Otherwise we'd have missed the first ferry to Lantau,
? as/so long as,provided/providing that,on condition that
? You can borrow my camera so/as long as
provided/providing that you handle it carefully,
on condition that
? This should be a positive statement,
? even if/though
? She won't tell us even though she knows the answer,
even if
? and/or (else)
? Take this medicine and you'll be all right tomorrow,
Hurry up or/or else you'll be late,
? (Let's) suppose,supposing,imagine,what if
? (Let's) suppose/Supposing it rained tomorrow,What would we do?
? (Let's) suppose/Supposing it had rained yesterday,What would we have done?
? Imagine you had a lot of money,What would you do with it?
Imagine you had won a lot if money,What would you do with it?
What if she told you the truth? Would you forgive her?
What if she had told you the truth? Would you have forgiven her?
? if it were not/had not been for,but for
? If it were not for her /But for her,I would not go to the party tomorrow,
? If it had not been for her /But for her,I wouldn't have gone to the party last night,
? without
Without his help,we wouldn't have succeeded,(= if it had not been for his help...)
? were to
? Were someone to try to break into the house,the alarm would be activated,(= if
someone tired to break into the house...)
? if so,if not
? Do you want to read this novel? If so (= if you do),you can have it,
If not (= if you do not,i will lend it to Melinda.)
Homework
? Exercise 34A on Pages 588-589
? Exercise 34B on Pages 592-594
? Exercise 34D on Pages 596-597
? Exercise 34E on Pages 597-598
? Exercise 34F on Pages 599-600
? Exercise 34G on Pages 600-601
? Exercise 34H on Pages 601-602
? 预习 第 35讲 （ 603-620页）
