這裡要講的是動詞的各式語態, 讓大家更清楚它們之間時段性的差別。

第一個要說的是現在完成式、現在完成進行式、過去完成式 與過去完成進行式:
It has rained for 3 days.(現在完成式)
已下了三天雨了。
It has been raining for 3 days.(現在完成進行式)
已下了三天雨了。(強調下的雨是持續性的)
這兩句現在完成式與現在完成進行式的例子意思基本上是一樣的, 唯一較維妙的差別是如果表達的人要強調下的雨是持續性的, 比較常會用現在完成進行式。
It had rained for 3 days.(過去完成式)
之前下了三天雨了。
It had been raining for 3 days.(過去完成進行式)
之前下了三天雨了。(強調下的雨是持續性的)
這兩句過去完成式與過去完成進行式的例子意思基本上是一樣的, 但如果表達的人要強調之前下的雨是持續性的, 也比較常會用過去完成進行式。
I have traveled to many countries.
我已旅遊過許多國家。
I have been traveling to many countries.
我已旅遊過許多國家。(強調這些旅遊是持續性的)
I had traveled to many countries.
我之前已旅遊過許多國家。(表示現在沒有在旅遊了)

再來講現在完成式許多人搞混的兩個例子,Have been to與Have been in的差別在哪?

I have been to Tokyo.
我有去過日本。(但現在人不在日本)
A: How many times have you been to United States?
你去過美國幾次啊?
B: I have been to United States twice.
我去過美國兩次。(現在不在美國）
I have been in Tokyo my whole life.
我一直在日本。
I have been in United States for 5 years.
我到現在已待美國５年了。

現在完成式 Vs. 過去式的例子

I have seen the movie.與Ｉsaw the movie.差別在哪裡呢?兩個都有我有看過這部電影的意思. 但有一個維妙的差別是現在完成式: I have seen the movie．意味著,表達的人記不清楚何時看過的; 而過去式：I saw the movie意味著表達的人很清楚何時看過的。

現在完成式 VS. 過去式 VS. 過去完成式 VS. 現在完成進行式

She has learned to speak English.(現在完成式)
She learned to speak English.(過去式)
She had learned to speak English.(過去完成式)
She has been learning to speak Enlgish.(現在完成進行式)
上面四個語態的差別在哪裡呢?
She has learned to speak English.與She learned to speak English.都意味她有學會說英文, 差別在She has learned to speak English.表示並不知道她是何時學的, She learned to speak English.表示她何時學的是清楚的。
She had learned to speak English.
意味著： 她知前有學會說英文,但現在忘記了;或是她已不在人世, 但她生前有學會說英文。
She has been learning to speak Enlgish.
她一直在學說英文。(表示她從前一段時間到現在都一直在學說英文)

Stacy has become very successful.
Stacy已變得很成功。(何時成功的不知道)
Stacy became very successful.
Stacy已變得很成功。(知道何時成功)
Stacy is becoming very successful.
Stacy正在變成功的過程當中。(還未完全成功)

過去分詞

I was confused by her speech.
我被她的演說給困惑到。
Confused是 過去分詞, 它與confuse的過去式confused是ㄧ樣拼法的。
The book was written by John.
這本書是John寫的。
Written這過去分詞與write的過去式wrote是不一樣的。
The work is done.
工作做完了。
Done是過去分詞, 它與do的過去式did也不一樣的。
你會發現以上三個過去分詞都是被動語態：
"was confused"
被困惑到。
"was written"
被寫。
"is done"
被完成。
雖然不是每一個過去分詞都是被動語態,但每一個被動語態都需要一個be動詞與過去分詞來組成。

過去分詞用在現在完成式或是過去完成式的時候就不是被動語態:

現在完成式: He has worked on the project for 2 weeks.
他已在這方案上動工了兩個星期。(這裡的過去分詞worked是主動語態)
過去完成式: It had rained for 4 days.
之前已下了4天雨。(這裡的過去分詞rained同樣是主動語態)

基本上, 只要有be動詞與過去分詞來組成的, 一定是被動語態:

我們用finish(完成), 來做一些例子:
It is finished.
它被完成了。
It is being finsihed.
它正在被完成中。
It has been finished.
它現在已被完成了。
It was being fisihed.
它之前正在被完成中。
It had been finsihed.
它之前已被完成了。
It will be finished.
它將會被完成。
這些be動詞加finished都是被完成的意思。

過去分詞當被動語態, 還可以用來造複合句子：

這兩句話：
Taipei 1O1 was completed in 2004.
台北101 2004年完工。(這裡的"was completed是被動語態)
Taipei 1O1 represents the modern architecture in Taipei City.
Taipei 101是台北市現代建築的最佳代表。
怎麼運用"was completed" 這個被動語態來把這兩句話, 連結成一句複合句呢?
Completed in 2004, Taipei 1O1 represents the modern architecture in Taipei City.
這裡你會發現原句"Taipei 1O1 was completed in 2004"放在這複合句裡的開頭時, "Taipei 101 was" 整個省略掉了。 所以被動語態是很好用的。
我們再來多用幾個例子:
Syntrend Creative Park is operated through investments made by Hon Hai Precision.
三創數位生活園區是鴻海公司投資經營。
Syntrend Creative Park represents the showcase for future transformation of the information industry giant in Taiwan.
三創數位生活園區代表了台灣資訊產業龍頭未來轉型的櫥窗。
這兩句話, 怎麼複合呢?
Operated through investments made by Hon Hai Precision, Syntrend Creative Park represents the showcase for future transformation of the information industry giant in Taiwan.
分詞片語裡, “Syntrend Creative Park is” 就省略了。
再一個例子：
Formosa Boulevard Station is ranked as one of the most beautiful subway stations in the world by various sources.
美麗島站被不同的來源評價為全世界最美麗的地鐵站之一。
Formosa Boulevard Station is at the intersection between the MRT red line and orange line.
美麗島站是紅線和橘線兩條捷運路線交會處。
複合句:
Ranked as one of the most beautiful subway stations in the world by various sources, Formosa Boulevard Station is at the intersection between the MRT red line and orange line.
這裡同樣的, 分詞片語裡 “Formosa Boulevard Station is”就省略了, 直接把被動語態的過去分詞“Ranked”排句前。
最後一個例子(特殊):
William's jacket is stored in the closet.
William的夾克存放在衣櫃裡。
William hasn't worn his jacket for a long time.
William已經很久沒有穿他的夾克了。
這兩句話, 怎麼複合呢?
Stored in the closet, William's jacket hasn't been worn for a long time.
"要注意的是", 我們不能說: Stored in the closet, William hasn't worn his jacket for a long time. 為什麼呢?
"Stored in the closet", 被存放在衣櫃的是William's Jacket而不是William 本身, 所以在分詞片語"Stored in the closet"後的主要子句裡,William's Jacket要放在最前面, 而不是William。 所以是:
Stored in the closet, William's jacket hasn't been worn for a long time. (正確）
Stored in the closet, William hasn't worn his jacket for a long time.（不正確)

最後再來講一個有趣的不及物動詞例子, 何謂不及物動詞呢? 不及物動詞任何情況是不會接受詞的,因此, 主動語態與被動語態是一樣的意思:

及物動詞, 比方說Write:
Mary wrote the book.
Mary寫了這本書。
也等於 The book was written by Mary.
這本書是Mary寫的。
"Write"這個及物動詞後面會加受詞。

現在我們講一個不及物動詞片語"sell out" (賣完)。
"Sell out"後面是不會加受詞的:
The books were sold out.
書被賣完了。
"Sold out" 後面不加受詞, 為何呢? 因為書是同時被賣方賣光也是被買方買光的, 你只能說像是:
The books were sold by the vendor.
書被賣方賣了。或是:
The books were bought by the customers.
書被買方買了。
但"Sold out"後面就不加受詞, 所以呢?
"The books were sold out."等於"The books sold out."
前句是被動語態, 後句是主動語態。所以像這句話：
"The books usually sell out in a flash." 等於"The books are usually sold out in a flash. "
這些書通常秒殺。
"Sell out in a flash" 這裡是賣東西秒殺的意思, 前句是主動語態,後句是被動語態。