[连词]
(1)引导条件:If the soup is too thick,add water.The garment will shrink,if washed.
If you happen to pass by a newsagents,can you get me the paper?
If only I hadn't pressed 'Delete.'
(2)if = when: if people look at him,he gets embarrassed.
语法结构
1 if分句, | + 分句
分句 | + if分句
If he had no money,he would sometimes sleep in the station.
Don't eat it if you don't like it.
谈论可能的情况及其结果
1a if分句(现在时), | + 分句(将来时)
If you're not careful,you'll break it.
The price of oil will go up if there's a war.
谈论将来可能的情况及其结果.(这种结构通常叫做第一条件句)
1b if分句(过去时), | + 分句(would/could 等)
If you were a parent,you'd understand how I feel.
I would vote for the Greens if I was allowed to vote.
谈论现在或将来不太可能的情况及其虚构的结果(这种结构通常叫做第二条件句)
1c if分句(过去完成时),| + 分句(would have/could have等)
It would've been more fun if it hadn't rained.
If you'd booked,we might've got a table.
谈论假想的过去情况及其结果(这种结构通常叫做第三条件句)
2 if | + so/not
Are you going into town?If so,can you give me a lift?
Check that the batteries are working.If not ,recharge them.
通过回指前面已经说到的情况来构成条件。
3 动词 | + if 分句
I asked her if she would like a dance.
Do you know if Jan is coming to work today?
转述一般疑问,或间接地问某人
搭配
if经常用在这些副词后面:(but) only,even.
Ahmed said he'll join us in the restaurant,but only if we let him pay.
Even if he tried,he'd never pass his exams.
if后经常接这些形容词:possible,necessary.
If possible,we'd like a room with a view.
The police have threatened to use force,if necessary,to remove the protestors.
在语法结构3里,经常放if前面的动词是:know,wonder,see,ask,doubt和remember,此外还有don't care,
don't mind,doesn't matter.
I wonder if dinner's ready.
See if this one fits.
I doubt if Dieter will agree.
I don't care if she's your sister:nobody says that to me.
Do you mind if I take this chair?
It doesn't matter if it rains because we can eat under the awning.
固定短语
'if I were you...' 我要是你的话
If I were you,I would forget all about him.
提供意见
if only ... 要是...
If only dad could have been here .He would have loved it.
If only it wasn't raining.
表示遗憾
'what if ...'如果...怎么样?
What if we ask your mother to babysit?
提出建议
'if you don't mind/if it's all right with you'如果你不介意的话
I'll close the window,if you don't mind.
If it's all right with you,I'd prefer the window seat.
提出要求