受動態

受動態は、行動を行なう人や物よりもそれを体験している人や物に興味を示すことに使われます。つまり、最も重要な人や物が文章の主語になるのです。

誰がその行動をしたかを知らない、または述べたくないので受動態を使う場合もあります。

正式な文書に受動態がよく使われます。能動態に変えると、文書がより明確になり読みやすくなります。

受動態	能動態
A great deal of meaning is conveyed by a few well-chosen words.	A few well-chosen words convey a great deal of meaning.
Our planet is wrapped in a mass of gases.	A mass of gases wrap around our planet.
Waste materials are disposed of in a variety of ways.	The city disposes of waste materials in a variety of ways.

受動態を使いながら、その行動をした人や物を述べたい場合は、前置詞byを用います。その行動をした人がわかっている時や、その人に興味がある場合、能動態を使うほうが良いでしょう。

受動態	能動態
"A Hard Day's Night" was written by the Beatles.	The Beatles wrote "A Hard Day's Night".
The movie ET was directed by Spielberg.	Spielberg directed the movie ET.
This house was built by my father.	My father built this house.

詳細は、すべての英語の動詞の時制の受動態とそれに相当する能動態をご覧ください

英語の受動態は二つの要素から成ります：
動詞 'to be'の適切な形態 + 過去分詞

肯定文	否定文	疑問文	否定疑問文
The house was built in 1899.	The house wasn't built in 1899.	Was the house built in 1899?	Wasn't the house built in 1899?
These houses were built in 1899.	These houses weren't built in 1899.	Were these houses built in 1899?	Weren't these houses built in 1899?

主語	+ to be (conjugated)	+ 過去分詞	+ 残りの文章
単純現在形
The house	is	cleaned	every day.
現在形継続
The house	is being	cleaned	at the moment.
単純過去形
The house	was	cleaned	yesterday.
過去形継続
The house	was being	cleaned	last week.
現在完了
The house	has been	cleaned	since you left.
過去完了
The house	had been	cleaned	before they arrived.
未来
The house	will be	cleaned	next week.
未来形継続
The house	will be being	cleaned	tomorrow.
条件付現在
The house	would be	cleaned	if they had visitors.
条件付過去
The house	would have been	cleaned	if it had been dirty.
不定詞
The house	must be	cleaned	before we arrive.