if三大虛擬語氣公式(if引導虛擬語氣三種時態(tài)表格)

虛擬語氣可以在狀語從句中表示讓步、方式和條件的句中出現(xiàn)，但他們體現(xiàn)的方式有所不同。這里談談if引導的條件狀語從句中的虛擬語氣。

1.虛擬語氣用在條件狀語從句中表示與事實相反的假設。通常由連詞if來引導。在表示對將來的虛擬時有下列形式。

主句用would/should/could/might加動詞原形，從句部分用should或者是were構(gòu)成。比如：

If you should need our help，you could tell us.如果你需要我們的幫助，請告訴我們。If it should happen，what would we do？如果發(fā)生的話，我們怎么辦？

2.當虛擬條件句表示與現(xiàn)在事實相反時，它的形式是：主句用would/should/could/might+動詞原形，從句部分用動詞的過去式或were。比如：

If I were you, I’d finish it on time.如果我是你，我就按時完成。If I were a bird, I would fly away.如果我是只鳥，我就飛走了。

3.當虛擬語氣表示對過去的假設時，句中的主句謂語用would/should/could/might+have+過去分詞，從句部分用had+過去分詞。比如：

I was so busy yesterday. If I had time, I would have called on you.我昨天太忙了。我要是有時間早就去看你了。

If we had got up earlier, we would have caught the train. 如果我們早點起床，我們就趕上火車了。

4.從句中的連詞if可以省掉，但從句要部分倒裝。前提條件是：從句中謂語動詞有were、had、should。這些詞可以提到從句最前面，也就是構(gòu)成了虛擬條件句的另一個句型。這也是虛擬語氣的考點之一。比如：

Were there no gravity, there would be no air around the earth.假如沒有重力，地球周圍就沒有空氣。

Were she in Beijing, she would help us.假如她在北京的話，她是會幫助我們的。

Had he time, he would help us to solve these problems.假如他有時間，他就會幫我們解決這些問題了。

Should they come to us, I should ask them some questions.假如他們真能來我們這里的話，我將問他們一些問題。

Had the checking up of the experimental data not taken so much time, we should have completed our work long ago.假如檢驗實驗數(shù)據(jù)不花那么多時間，那末我們早就完成這項工作了。

Were it not for the leadership of the Party, we could not live a happy life.要不是黨的領導，我們不可能過幸福生活。