1.if引導的條件從句,有時後接only以加強其語氣,表示說話人非常盼望某人提出的條件能夠實現。
2.if可引導讓步狀語從句,作“雖然,即使”解,常和even連用。
3.if作為從屬連詞,可引導條件狀語從句、讓步狀語從句和名詞從句。
4.if引導條件狀語從句,從句可為真實條件從句,也可為虛擬條件從句。如為真實條件從句,謂語用陳述語氣,表示可能性很大,作“假使”“如果”解,通常用一般現在時代替一般將來時; 如果if從句中用will,表示意願。從句如為虛擬條件從句,謂語動詞要用虛擬語氣,表示可能性不大或與過去事實相反,作“要是,假如”解。可指過去的情況,也可指現在和將來的情況。指將來情況時可用were to或should。在現代口語中,一、三人稱後常用was代替were。if引導的虛擬條件句中,助動詞were,should,had可以移至主語前,此時if可省略。
5.if引導的條件從句中可以省略be和主語。
6.if可引導名詞性從句,作“是否”解,常放在ask, doubt, know, learn, see, wonder等動詞後。一般用在口語中,而且不能用於句首。
if的用法例句：
1. If you wait, all that happens is that you get older.
如果你等待，發生的只有變老。
2. If you love life, life will love you back.
熱愛生活，生活也會厚愛你。
3. If you're not satisfied with the life you're living, don't just complain. Do something about it.
對於現況的不滿，不能只是抱怨，要有勇氣作出改變。
4. If you're lonely when you're alone, you're in bad company.--Jean Paul Sartre
如果你獨處時感到寂寞，說明沒有把自己陪好。
5. Friendship means understanding, not agreement. It means forgiveness, not forgetting.It means the memories last, even if contact is lost.
友情是理解，不是妥協;是原諒，不是遺忘。即使不聯絡，感情依然在。
6. You have to do everything you can. You have to work your hardest. And if you do, if you stay positive, then you have a shot at a silver lining.
你必須全力以赴，最大限度地去努力。如果你這麼做，並且保持樂觀，你就會看見烏雲背後的幸福線。
7. The house seemed muted, hushed as if it had been deserted.
房子裡似乎悄然無聲，安靜得好像已經沒人在住一樣。
8. He'd phoned Laura to see if she was better.
他打電話給勞拉看她是不是好些了。
9. Things might have been different if I'd talked a bit more.
如果當時我再多說一點的話，結果或許會不一樣。
10. If your skin becomes red, sore or very scaly, consult your doctor.
如果皮膚髮紅、瘙癢或脫皮，要向醫生諮詢。
11. If you build more plastics into cars, the car lasts longer.
如果汽車採用更多塑膠元件，壽命會更長一些。
12. More people would be attracted to cycling if conditions were right.
如果天氣適宜，會有更多的人被吸引到騎腳踏車的行列中來。
13. But legal experts are not sure if such a charge can stick.
但法律專家們不能肯定這一指控是否成立。
14. If they value these data, let them pay for them.
他們要是看重這些資料，就讓他們出錢買。
15. They get angry if they think they are being treated disrespectfully.
他們要是覺得受到了怠慢，就會大動肝火。
1.if引導的條件從句,有時後接only以加強其語氣,表示說話人非常盼望某人提出的條件能夠實現。
2.if可引導讓步狀語從句,作“雖然,即使”解,常和even連用。
3.if作為從屬連詞,可引導條件狀語從句、讓步狀語從句和名詞從句。
4.if引導條件狀語從句,從句可為真實條件從句,也可為虛擬條件從句。如為真實條件從句,謂語用陳述語氣,表示可能性很大,作“假使”“如果”解,通常用一般現在時代替一般將來時; 如果if從句中用will,表示意願。從句如為虛擬條件從句,謂語動詞要用虛擬語氣,表示可能性不大或與過去事實相反,作“要是,假如”解。可指過去的情況,也可指現在和將來的情況。指將來情況時可用were to或should。在現代口語中,一、三人稱後常用was代替were。if引導的虛擬條件句中,助動詞were,should,had可以移至主語前,此時if可省略。
5.if引導的條件從句中可以省略be和主語。
6.if可引導名詞性從句,作“是否”解,常放在ask, doubt, know, learn, see, wonder等動詞後。一般用在口語中,而且不能用於句首。
if的用法例句：
1. If you wait, all that happens is that you get older.
如果你等待，發生的只有變老。
2. If you love life, life will love you back.
熱愛生活，生活也會厚愛你。
3. If you're not satisfied with the life you're living, don't just complain. Do something about it.
對於現況的不滿，不能只是抱怨，要有勇氣作出改變。
4. If you're lonely when you're alone, you're in bad company.--Jean Paul Sartre
如果你獨處時感到寂寞，說明沒有把自己陪好。
5. Friendship means understanding, not agreement. It means forgiveness, not forgetting.It means the memories last, even if contact is lost.
友情是理解，不是妥協;是原諒，不是遺忘。即使不聯絡，感情依然在。
6. You have to do everything you can. You have to work your hardest. And if you do, if you stay positive, then you have a shot at a silver lining.
你必須全力以赴，最大限度地去努力。如果你這麼做，並且保持樂觀，你就會看見烏雲背後的幸福線。
7. The house seemed muted, hushed as if it had been deserted.
房子裡似乎悄然無聲，安靜得好像已經沒人在住一樣。
8. He'd phoned Laura to see if she was better.
他打電話給勞拉看她是不是好些了。
9. Things might have been different if I'd talked a bit more.
如果當時我再多說一點的話，結果或許會不一樣。
10. If your skin becomes red, sore or very scaly, consult your doctor.
如果皮膚髮紅、瘙癢或脫皮，要向醫生諮詢。
11. If you build more plastics into cars, the car lasts longer.
如果汽車採用更多塑膠元件，壽命會更長一些。
12. More people would be attracted to cycling if conditions were right.
如果天氣適宜，會有更多的人被吸引到騎腳踏車的行列中來。
13. But legal experts are not sure if such a charge can stick.
但法律專家們不能肯定這一指控是否成立。
14. If they value these data, let them pay for them.
他們要是看重這些資料，就讓他們出錢買。
15. They get angry if they think they are being treated disrespectfully.
他們要是覺得受到了怠慢，就會大動肝火。