英語動(dòng)詞有主動(dòng)語態(tài)(the active voice)和被動(dòng)語態(tài)(the passive voice)兩種形式。如果主語是謂語動(dòng)詞的主宰，這就是主動(dòng)語態(tài);如果賓語成為動(dòng)作的執(zhí)行者，這就是被動(dòng)語態(tài)。

在下列兩個(gè)句子中，(a)是主動(dòng)語態(tài)，(b)是被動(dòng)語態(tài)。

① a. I have just bought a new book.

b. A new book has just been bought by me.

② a. Tom will invite you to dinner.

b. You will be invited to dinner by Tom.

主動(dòng)轉(zhuǎn)被動(dòng)語態(tài)的步驟

從主動(dòng)語態(tài)轉(zhuǎn)換為被動(dòng)語態(tài)時(shí)，必須按照下列步驟進(jìn)行：

⒈把謂語動(dòng)詞后頭的賓語移到句首當(dāng)主語。如果沒有賓語或者不是賓語的句子成分， 就沒有新主語;這句話也就不能有被動(dòng)語態(tài)了。

⒉如果有兩個(gè)賓語(即直接賓語和間接賓語)，只要把其中一個(gè)變成主語即可， 其他一個(gè)保留在原位。

⒊用助動(dòng)詞“be + 過去分詞”的動(dòng)詞形式，并和主語的人稱、數(shù)目配合;動(dòng)詞時(shí)態(tài)也要和主動(dòng)語態(tài)里的配合。

⒋如果主動(dòng)語態(tài)中有語氣動(dòng)詞(如：must, can, should)等，就以這個(gè)語氣動(dòng)詞和“be + 過去分詞”連用。

⒌把主動(dòng)語態(tài)里的主語移到句末， 但要在它前面加上介詞“by ”。通常，這個(gè)“by + 主語”的短語，都被省略了。

⒍如果謂語動(dòng)詞是片語動(dòng)詞(the phrasal verb)的話， 就要把片語動(dòng)詞當(dāng)一個(gè)單位處理。例如：

③ a. We must do the work.

b. The work must be done (by us)。

④ a. John gave Anne a pen.

b. Anne was given a pen by John 或 A pen was given to Anne by John.

⑤ a. They have put off the meeting.

b. They meeting has been put off.

使用被動(dòng)語態(tài)的情況

一般上說，我們用主動(dòng)語態(tài)的時(shí)候多，用被動(dòng)語態(tài)的時(shí)候少。然而，如果我們不知道誰是動(dòng)作的執(zhí)行者，我們只有被動(dòng)語態(tài)這條路可走：

⑥ A cat was knocked down.

⑦ Electricity is widely used in all cities.

⑧ The annual sports meet may be held in three months.

此外，在下列情況下，也最好用被動(dòng)語態(tài)：

⒈賓語比主語重要，必須突出，如：

⑨ A thief was arrested.

⑩ The waste paper has been burnt.

如果把⑨和⑩改為主動(dòng)語態(tài)，就平淡乏味了：

△The police arrested a thief.

△Someone has burnt the waste paper.

⒉不方便提到主語;在此情況下， 常用“it”來引導(dǎo)，如：

11. It is said that the government will raise the income tax.

⒊有些動(dòng)詞多以被動(dòng)語態(tài)出現(xiàn)，如：

12. All are expected to come early.

13. The report was based on the findings of a survey.