文档介绍：授课教师：王元元
if
if
如果
（引导条件状从，符合主将从现原则）
是否
whether
≈
. If it is sunny tommorrow, i will go fishing with you.
宾从中的"是否"
if=whether
. I don't know whether (if) he can come.
…or (not) "是否"用whether ，表从和同位语从句中"是否"用whether
即只能用whether的三种情况：
if≠whether
有关if的词组的考查： 1. if only
所引导的从句用虚拟语气
. If only i were you.（与现在相反）
If only i had studied hard.（与过去相反）
主句用倒装语序
. Only if you study hard can you pass the exams.
Only if you come with me will i go home.
2. only if
尽管,即使
不与but连用
. Even if he is little, he knows a lot.
They will stand by you even if you don't succeed.
好像
所引导的从句与实际情况不符时用虚拟语气
. He talks as if he knew where she was．（与现在相反）
The girl listened as if she had been turned to stone．（与过去相反）
if =even though
if = as though
如果可能的话
. If possible， i will always be with you .
如果有必要的话
. If necessary， i can tell you my telephone number.
如果这样的话
. Are you free this evening?If so,let's go out for a meal.
如果不这样的话
. Are you free this evening?If not, see you tomorrow.
5. if possible
if necessary
if so
if not
练****题： 1. If he ________(study) hard, he will get good grades. 2. I want to know if Mary _______(go) to the party tomorrow. 3. There is no doubt_______he can come. 4. There is some doubt ________ he can come. 5. The t