广东省惠州市区号:If的用法

1.可引导条件状语从句。主句用一般将来式，从句要用一般现在式表将来式。
I will not go out if it rains tomorrow.

初中的话就是假设吧
如果……就……

if
[if]
conj.
(表条件)如果, (表假设)要是, 是否, 即使
n.
条件, 设想

if
[If]
conj.
如果；假如
If you ask him, he will help you.
如果你向他请求，他会帮助你。
"If need be, we'll work all night."
"如果需要,我们就干个通宵。"
即使；虽然
We'll go even if it rains.
即使下雨我们也要去。
是否
She asked if that was enough.
她问那是否够了。
He asked if Mr Gilbert's operation had been successful and the doctor told him that it had been.
"他问吉尔伯特先生的手术是否成功,医生告诉他,手术是成功的。"

if
n.
条件，限制条件
I don't want any ifs and buts; do it at once.
"我不想听任何要推延的理由,立刻干吧。"
Your investigation report seems to have too many ifs.
你的调查报告似乎假设太多了一些。

if
AHD:[¹f]
D.J.:[if]
K.K.:[!f]
conj.
In the event that:
如果，倘若在…的情况下：
If I were to go, I would be late.
倘若我去，就要迟到
Granting that:
假设，如果：
If that is true, what should we do?
假设那是真的我们该怎么办呢?
On the condition that:
如果，只要在某种条件下：
She will play the piano only if she is paid.
只有付给她报酬，她才愿意演奏钢琴
Although possibly; even though:
虽然；即使：
It is a handsome if useless trinket.
虽然无用却很漂亮的小饰物
Whether:
是否：
Ask if he plans to come to the meeting.
问问他是否要来参加会议
Used to introduce an exclamatory clause, indicating a wish:
但愿，要是…该多好啊用来引出一个表达愿望的感叹句，表达一个愿望：
If they had only come earlier!
如果他们早来一步该多好啊!
if
n.
A possibility, condition, or stipulation:
条件可能性、条件或设想：
There will be no ifs, ands, or buts in this matter.
这件事不允许有假设、拖延或反对

Middle English
中古英语
fromOld English gif
源自古英语 gif
*See Also : i- In Appendix

In informal writing both if and whether are standard in their use to introduce a clause indicating uncertainty after a verb such as ask, doubt, know, learn, or see:
在非正式的写作中，可以使用 if或 wether两个词来表达不定性，两者都算标准，例如 ask,doubt,know,learn,或see这样的动词后：
We shall soon learn whether (or if) it is true.In such contexts, however, the use of if can sometimes create ambiguities. Depending on the intended meaning, the sentence Let her know if she is invited might be better paraphrased as Let her know whether she is invitedor If she is invited, let her know. · In conditional sentences the clause introduced by if may contain either a past subjunctive verb ( if I were going) or an indicative verb ( if I am going; if I was going), depending on the intended meaning. According to the traditional rule, the subjunctive should be used to describe an occurrence that is presupposed to be contrary to fact, as in if I were ten years youngeror if Napoleon had won at Waterloo.The main verb of such a sentence must then contain the modal verb would or (less frequently) should:
我们很快就会知道这是否（或 if) 是真实的。不过在这种情况下，用 if就可能会造成歧义。 Let her know if she is invited 这句话最好根据所要表达的意思，分开说成 告诉她她是否被邀请了或 如果她被邀请了，就让她知道两句话。用 if引起的条件状语从句中，可以含有一个过去式的虚拟动词( 倘若我去)或一个一般陈述动词( 如果我就去；如果我去了)，这得依据所要表达的意思而定。根据正统的原则，虚拟语气用来表达一个与事实相反的假设，例如 如果我再年轻十岁或者 如果拿破仑在滑铁卢战役中获胜。于是在这样的句子里，主要动词必须包含情态动词 会或（在较少情况下）应该：
If America were still a British colony, we would have an anthem that human voices could sing.
如果美国现在还是英国的殖民地，我们就会有一支人人都会唱的国歌。
If I were the President, I should (or would) declare November 1 a national holiday.When the situation described by the if clause is not presupposed to be false, however, that clause must contain an indicative verb, and the choice of verb in the main clause will depend on the intended meaning:
如果我是总统，我就（或 会) 宣布十一月一日为国家休假日。而只要 if引起的从句描述的条件不是事先就被认为是不可能的，从句中就必须使用直陈动词，而主句中词的形式就要依所要表达的意义而定：
If Hamlet was really written by Marlowe, as many have argued, then we have underestimated Marlowe's genius.
如果就象很多人猜测的那样，《哈姆雷特》一剧是由马洛写的，那我们就一直低估了马洛的才能。
If Kevin was out all day, then it makes sense that he couldn't answer the phone.Note also that the presence of the modal verb would in the main clause should not be taken as a sign that the verb in the if clause must be in the subjunctive, if the content of that clause is not presupposed to be false:
如果确实一直在外面，打电话找不着他是很正常的。另须注意，在主句中使用情态动词 would并不表明 if从句中一定使用虚拟语气，因为从句的内容并不一定原先就认为是错误的：
If I was (not were) to accept their offer—which I'm still considering—I would have to start the new job on May 2.
如果我去（不是 were)接受他们的盛情——我还在这样考虑——那么我必须在5月2日开始新工作。
He would always call her from the office if he was (not were) going to be late for dinner. · Again according to the traditional rule, the subjunctive is not correctly used following verbs such as ask or wonder in if clauses that express indirect questions, even if the content of the question is presumed to be contrary to fact:
如果他（不是 were) 晚餐会迟到，就会从办公室打电话给她。 · 另外还是根据传统规则，在动词 ask或 wonder中 if引导的间接问句，即使其内容被认为与事实相反，也不能使用虚拟语气：
We wondered if dinner was (not were) included in the room price.
我们想知道晚餐费用是否被（不是 were)包括在房间费中。
Some of the people we met even asked us if California was (not were) an island. · With all deference to the traditional rules governing the use of the subjunctive, it should be noted that a survey of the prose of reputable writers over the past 200 years would reveal a persistent tendency to use the indicative was where the traditional rule would require the subjunctive were. A sentence beginning If I was the only boy in the world, while not strictly correct, is wholly unremarkable. But the corresponding practice of using the subjunctive in place of the indicative may be labeled a hypercorrection. · In spoken English there is a growing tendency to use would have in place of the subjunctive in contrary-to-fact clauses, as in if I would have been the President,but this usage is still widely considered incorrect.
我们碰到的一些人甚至问我们加利福尼亚是否是（不用 were) 一个岛屿。 在与指导虚拟语气使用方法的传统规则相冲突的一系列不同用法中，我们应注意到一项对过去200年散文作家的调查显示，在传统语法要求使用虚拟式的 were的情况下，有一种持久的使用直陈式 was的趋势。一句用 假如我是世界上唯一的男孩开头的句子不会引起人们的注意。而一定要把其中的直陈式换成虚拟式就显得矫正过了头。在英语口语中，在与事实相反的从句中，使用 would have一词的趋势有所增加，例如 如果我会是总统，但这种用法仍然被大多数人认为是不正确的
See: doubt should wish

IF or i.f.
abbr.
Intermediate frequency.
中波

if
[if]
conj.
[表示条件, 假设]如果, 要是; 假如
[表示让步]虽然; 即使
是否, 是不是
(＝whenever)无论何时; 当
[表示愿望, 感叹]要是....多好
If weather permits....
(常略作I.W.P)如果天气好的话....
I'll do it if I die in the attempt.
即使会丧命我也要试一下。
Ask if he is at home.
问一问他在不在家。
If I do not understand what he says, I always ask him.
我不懂他的话时, 总是去问他。
If I haven't lost my watch!
我的表要是不丢该多好!
If I only knew!
要是我知道该多好。

if
[if]
n.
条件; 设想
ifs and buts
拖延的原因
Your argument seems to have too many ifs.
你的论据似乎假设太多了一些。
I don't want ifs and buts; swallow your medicine at once.
我可不听你泡蘑菇, 马上吞下你的药。

if and when
如果, 万一
If ifs and ans were pots and pans, there'd be no trade for tinkers.
[谚]如果种种“假如”能够变成深锅和浅锅, 补锅匠就没有生意了。(意思是:如果人们的主观愿望都能实现, 天下就太平了)
if only
只要; 要是....就好, 但愿

if

If is talking about a future consequence
For example: If we could live on the moon we might have more room on earth.
如果

if
if
AHD:[¹f]
D.J.[if]
K.K.[!f]
conj.（连接词）
In the event that:
如果，倘若：在…的情况下：
If I were to go, I would be late.
倘若我去，就要迟到
Granting that:
假设，如果：
If that is true, what should we do?
假设那是真的我们该怎么办呢?
On the condition that:
如果，只要：在某种条件下：
She will play the piano only if she is paid.
只有付给她报酬，她才愿意演奏钢琴
Although possibly; even though:
虽然；即使：
It is a handsome if useless trinket.
虽然无用却很漂亮的小饰物
Whether:
是否：
Ask if he plans to come to the meeting.
问问他是否要来参加会议
Used to introduce an exclamatory clause, indicating a wish:
但愿，要是…该多好啊：用来引出一个表达愿望的感叹句，表达一个愿望：
If they had only come earlier!
如果他们早来一步该多好啊!
n.（名词）
A possibility, condition, or stipulation:
条件：可能性、条件或设想：
There will be no ifs, ands, or buts in this matter.
这件事不允许有假设、拖延或反对

Middle English
中古英语
from Old English gif * see i-
源自 古英语 gif *参见 i-

In informal writing both if and whether are standard in their use to introduce a clause indicating uncertainty after a verb such as ask, doubt, know, learn, or see:
在非正式的写作中，可以使用if 或 wether 两个词来表达不定性，两者都算标准，例如 ask,doubt,know,learn, 或 see这样的动词后：
We shall soon learn whether (or if ) it is true.
我们很快就会知道这是否（或 if ) 是真实的。
In such contexts, however, the use of if can sometimes create ambiguities. Depending on the intended meaning, the sentence Let her know if she is invited might be better paraphrased as Let her know whether she is invited or If she is invited, let her know. · In conditional sentences the clause introduced by if may contain either a past subjunctive verb (if I were going ) or an indicative verb ( if I am going; if I was going ), depending on the intended meaning. According to the traditional rule, the subjunctive should be used to describe an occurrence that is presupposed to be contrary to fact, as in if I were ten years younger or if Napoleon had won at Waterloo. The main verb of such a sentence must then contain the modal verb would or (less frequently) should:
不过在这种情况下，用if 就可能会造成歧义。 Let her know if she is invited 这句话最好根据所要表达的意思， 分开说成告诉她她是否被邀请了 或 如果她被邀请了，就让她知道 两句话。 用if 引起的条件状语从句中， 可以含有一个过去式的虚拟动词(倘若我去 )或一个一般陈述动词( 如果我就去；如果我去了 )， 这得依据所要表达的意思而定。根据正统的原则，虚拟语气用来表达一个与事实相反的假设，例如如果我再年轻十岁 或者 如果拿破仑在滑铁卢战役中获胜。 于是在这样的句子里，主要动词必须包含情态动词会 或（在较少情况下） 应该：
If America were still a British colony,
如果美国现在还是英国的殖民地，
we would have an anthem that human voices could sing.
我们就会有一支人人都会唱的国歌。
If I were the President,
如果我是总统，
I should (or would ) declare November 1 a national holiday. When the situation described by the if clause is not presupposed to be false, however, that clause must contain an indicative verb, and the choice of verb in the main clause will depend on the intended meaning:
我就（或 会 ) 宣布十一月一日为国家休假日。 而只要if 引起的从句描述的条件不是事先就被认为是不可能的， 从句中就必须使用直陈动词，而主句中词的形式就要依所要表达的意义而定：
If Hamlet was really written by Marlowe, as many have argued, then we have underestimated Marlowe's genius.
如果就象很多人猜测的那样，《哈姆雷特》一剧是由马洛写的，那我们就一直低估了马洛的才能。
If Kevin was out all day, then it makes sense that he couldn't answer the phone.
如果确实一直在外面，打电话找不着他是很正常的。
Note also that the presence of the modal verb would in the main clause should not be taken as a sign that the verb in the if clause must be in the subjunctive, if the content of that clause is not presupposed to be false:
另须注意，在主句中使用情态动词would 并不表明 if 从句中一定使用虚拟语气，因为从句的内容并不一定原先就认为是错误的：
If I was (not were ) to accept their offer—which I'm still considering—I would have to start the new job on May 2.
如果我去（不是 were ) 接受他们的盛情——我还在这样考虑——那么我必须在5月2日开始新工作。
He would always call her from the office if he was (not were ) going to be late for dinner. ·
如果他（不是 were ) 晚餐会迟到，就会从办公室打电话给她。 ·
Again according to the traditional rule, the subjunctive is not correctly used following verbs such as ask or wonder in if clauses that express indirect questions, even if the content of the question is presumed to be contrary to fact:
另外还是根据传统规则，在动词ask 或 wonder 中 if 引导的间接问句， 即使其内容被认为与事实相反，也不能使用虚拟语气：
We wondered if dinner was (not were ) included in the room price.
我们想知道晚餐费用是否被（不是 were ) 包括在房间费中。
Some of the people we met even asked us if California was (not were ) an island. ·
我们碰到的一些人甚至问我们加利福尼亚是否是（不用 were ) 一个岛屿。
With all deference to the traditional rules governing the use of the subjunctive, it should be noted that a survey of the prose of reputable writers over the past 200 years would reveal a persistent tendency to use the indicative was where the traditional rule would require the subjunctive were. A sentence beginning If I was the only boy in the world, while not strictly correct, is wholly unremarkable. But the corresponding practice of using the subjunctive in place of the indicative may be labeled a hypercorrection. · In spoken English there is a growing tendency to use would have in place of the subjunctive in contrary-to-fact clauses, as in if I would have been the President, but this usage is still widely considered incorrect.See Usage Note at doubt, should, wish
在与指导虚拟语气使用方法的传统规则相冲突的一系列不同用法中，我们应注意到一项对过去200年散文作家的调查显示，在传统语法要求使用虚拟式的were 的情况下，有一种持久的使用直陈式 was 的趋势。 一句用假如我是世界上唯一的男孩 开头的句子不会引起人们的注意。 而一定要把其中的直陈式换成虚拟式就显得矫正过了头。在英语口语中，在与事实相反的从句中，使用would have 一词的趋势有所增加， 例如如果我会是总统， 但这种用法仍然被大多数人认为是不正确的参见 doubt， should， wish

IF
IF 或 i.f.
abbr.（略语）
Intermediate frequency.
中波

if
[If]
conj.
如果；假如
If you ask him, he will help you.
如果你向他请求，他会帮助你。
"If need be, we'll work all night."
"如果需要,我们就干个通宵。"
即使；虽然
We'll go even if it rains.
即使下雨我们也要去。
是否
She asked if that was enough.
她问那是否够了。
He asked if Mr Gilbert's operation had been successful and the doctor told him that it had been.
"他问吉尔伯特先生的手术是否成功,医生告诉他,手术是成功的。"

if
n.
条件，限制条件
I don't want any ifs and buts; do it at once.
"我不想听任何要推延的理由,立刻干吧。"
Your investigation report seems to have too many ifs.
你的调查报告似乎假设太多了一些。

if
<古英语 gif

if,whether这两个词都能引出宾语从句，词义是“是否”。
if 为口语体。有时两个词可以通用，但是当所引出的从句为介词宾语或不定式短语时，则只能用whether
My wife wants to know if Mary needs any help.
我妻子想知道玛丽是否需要帮忙。
He wants to know if you are tired.
他想知道你是否累了。
下面两句中的whether 都可以用if 代替
I wonder whether she will be able to come.
我怀疑她是否能来。
I don't know whether it's large enough.
我不知道这是否够大。
但下面各句中只能用whether
You haven't answered the question of whether you'll go with us or not.
你还没有回答你是否跟我们去的问题。
I don't know whether to go or stay.
我不知道是去还是留。

if
conj.(表条件)如果, (表假设)要是, 是否, 即使
n.条件, 设想

What if …?

（1）如果…该怎么办呢？

例如：What if you should fail?

假如你失败了该怎么办呢？

可以把此句加以补充为What would happen if…?

假如他失败了又有什么关系？

（2）如果…又有什么关系？

（＝What though …? ）

What if he fails?

假如他失败了又有什么关系？

可把此句补充为What （does it matter）if…