如果你看到下列的句子，你會認為它們是正確的還是錯的呢？
1.I wish I were a bird.
request that you be here tomorrow.
也許你會說:"哈哈，第一句的 I were 錯了，應該是 I was；而第二句中的 you be是什麼東東呀？不是 you are, 也不是 you will be, 什麼 you be?!"其實上面的句子都是一種稱為 Subjunctive 型別的句子。Subjunctive Mood 有的書譯為"假設語氣"，雖不很貼切；但在相當大的程度上，告訴我們這種句子的特點。Subjunctive Mood中文譯作"虛擬語氣"，似乎不及"假設語氣"那麼容易明白。它是一種動詞形式，表示說話人的某種假設、願望、懷疑、猜測、建議等含義。基本上，虛擬語氣可分為虛擬現在(Subjunctive Present)和虛擬過去(Subjunctive Past)兩種；但它們和時態(Tenses)上所指的現在時態(Present Tense)和過去時態(Past Tense)是有所不同的。
一、虛擬現在(Subjunctive Present):虛擬現在的句子，在任何時候都要用動詞的.原形(root form)，就算是第三人稱(he,she, it)也是如此。如：
1.1 現在時態(Simple Present): (右邊為虛擬語氣)
I work ---- I work
you work ---- you work
he works ---- he work (注意到了嗎，是 work，不是 works)
she works ---- she work (不是 she works 喔）
it works ---- it work (同樣不是 it works 喔)
we work ---- we work
they work ---- they work
1.2 現在進行時態(Present Continuous):(右邊為虛擬語氣）
I am working ---- I be working (注意用的是 be，怪怪的!)
you are working ---- you be working
he is working ---- he be working
she is working ---- she be working
it is working ---- it be working
we are working ---- we be working
they are woring ---- they be working
1.3 現在完成時態(Present Perfect):(右邊為虛擬語氣)
I have worked ---- I have worked
you have worked ---- you have worked
he has worked ----- he have worked (用的還是have喔)
she has worked ---- she have worked
it has worked ---- it have worked
we have worked ---- we have worked
they have worked ---- they have worked
1.4 現在完成進行時態(Present Perfect Continuous):(右邊為虛擬語氣)
I have been working ---- I have been working
you have been working ---- you have been working
he has been working ---- he have been working (是 he have, 不是 he has )
she has been working ---- she have been working
it has been working --- it have been working
we have been working ---- we have been working
they have been working ---- they have been working
二、虛擬過去(Subjunctive Past)虛擬過去的動詞無論在什麼情況之下都要用過去複數形式。如：動詞 be，在虛擬過去中要用 were。
2.1 過去時態(Simple Past):(右邊為虛擬語氣)
I worked ---- I worked
you worked ---- you worked
he worked ---- he worked
she worked ---- she worked
it worked ---- it worked
we worked ---- we worked
they worked ---- they worked
2.2 過去進行時態(Past Continuous):(右邊為虛擬語氣)
I was working ---- I were working （注意是 I were）
you were working ---- you were working
he was working ---- he were working (是 he were 喔)
she was working ---- she were working
it was working ---- it were working
we were working ---- we were working
they were working ---- they were working
2.3 過去完成時態(Past Perfect):(右邊為虛擬語氣)
I had worked ---- I had worked
you had worked ---- you had worked
he had worked ---- he had worked
she had worked ---- she had worked
it had worked ---- it had worked
we had worked ---- we had worked
they had worked ---- they had worked
(耶，全部都用 had ! )
2.4 過去完成進行時態(Past Perfect Continuous):(右邊為虛擬語氣)
I had been working ---- I had been working
you had been working ---- you had been working
he had been working ---- he had been working
she had been working ---- she had been working
it had been working ---- it had been working
we had been working ---- we had been working
they had been working ---- they had been working
