passive voice 問題

通常來說，要看一個動詞是否有passive voice，就要看這個動詞是否能作及物動詞，如：

love可以作及物動詞，所以，我們會說I love you
就因為它可作及物動詞，故就有被動語氣，如：You are loved.

但有些動詞，它只可作不及物動詞，那它就沒有被動語氣，如：

He died.這個die沒有及物動詞用法，故也就沒有passive voice.
Fish swim.這個swim是不及物動詞，故也就沒有passive voice.

當然有些動詞，在不同的意思下，一時作及物，一時作不及物；那時就要看動詞的意思而定，如：

Horses run(run作跑的意思，是不及物動詞）
He run his business very well（run作經營是及物動詞，所以有passive voice ）

還有一些不及物動詞，加上介詞或副詞後成為片語動詞，會變成及物動詞，這時，也會有passive voice

如：look down on如:
　　Why are mentally retarded people always looked down on?

希望幫到你！

根據你上一個問題，我猜你是想問「在文法上，一個動詞是否有 passive voice」，而不是「在內容上，一個動詞是否有 passive voice」吧？

很遺憾地，並沒有一個方法／捷徑去得知在文法上一個動詞是否具有 passive voice，這要靠背誦，多看些文章，慢慢讓自己記住哪些動詞有 passive voice，哪些無。

找了一個關於「不具備 passive voice 之動詞」的 list，希望對你有用：

http://www.grammar-quizzes.com/passive1d.html

既然叫作「被動」語式，便要看那個動詞/動作是不可以「被」做出來。直接的回答是按詞的意思/表達需要來決定能不寫出一句被動語。

你舉的例子appear本身語義一定是一個主體出現(這動作)，並不會有「被出現」或由主體出現了一個受體，反過來寫被動式。

或者可以說不及物動詞一定不會有被動語態吧。

Present tense

1) I see a movie
A movie is seen by me - Passive voice


2) Mary buys a new handbag.
A new handbay is bought by Mary.

Past tense

1) I saw Mary on my way home yesterday.
Mary was seen by me on my way home yesterday.


Present Perfect tense (Past perfect tense)
1) I have seen Mary on my way home ( have / has - had)
Mary has been seen by me on my way home

2) They have played basket ball
The basket ball has been played by them

Present continuous tense
I am watching TV
TV is being watched by me

She/ He is watching TV
TV is being watched by her/ him

They/you/we are playing football
The football is being played by them/you/ us.

The dog is barking at the strangers
The strangers are being barked by the dog.

The dress is sold = Passvie voice in present tense
The dress was sold = Passive voice in past tense