能動文では主語が動作を行う：Maria wrote the letter.（Maria が手紙を書いた。）受動文では主語が動作を受ける：The letter was written by Maria.（手紙は Maria によって書かれた。）動作を受ける人や物が文の中心になる。
受動態は日常の多くの場面で役立つ。誰がしたかわからないとき、それが重要でないとき、あるいは行為者より結果のほうが大切なときに使う。
基本の形： 主語 + am / is / are（現在形）または was / were（過去形）+ 過去分詞 → English is spoken here. The window was broken.
受動態は他動詞——能動文で目的語を取る動詞（speak English、break the window、check the locks）——にしか使えない。arrive、happen、sleep などの自動詞は目的語を持たないため、受動態はない。
なぜ受動態を使うのか
受動態を使う理由は主に3つある：
- 行為者が不明： My phone was stolen last night.（誰が盗んだかわからない）
- 行為者が明らかまたは重要でない： She was born in 1998. English is taught in schools worldwide.
- 結果のほうが行為者より重要： The bridge is inspected every year. This song was recorded in one take.
ニュース記事・学術的な文章・説明書など、フォーマルな文章では受動態が特によく使われる。誰がしたかではなく、何が起きたかに焦点が当たるからだ。
現在形の受動態
Am / is / are + 過去分詞
現在形の受動態は、定期的な状態・習慣・事実を表す。能動態の現在形と同じ場面だが、動作を受ける側に焦点が当たる。
| 能動態 | 受動態 |
|---|---|
| Farmers grow coffee in Brazil. | Coffee is grown in Brazil. |
| Someone checks the locks every night. | The locks are checked every night. |
| The team uses this software. | This software is used by the team. |
am / is / are の選択は受動文の主語によって決まる：
| 主語 | be動詞 | 過去分詞 | 例文 |
|---|---|---|---|
| I | am | invited | I am invited to the party. |
| he / she / it | is | checked | It is checked daily. |
| we / you / they | are | made | These shoes are made in Italy. |
過去形の受動態
Was / were + 過去分詞
過去形の受動態は、過去に完了した動作を表す。主語に何が起きたかに焦点が当たる。
| 能動態 | 受動態 |
|---|---|
| Someone built this bridge in 1920. | This bridge was built in 1920. |
| They cancelled the concert. | The concert was cancelled. |
| Workers made the first cars by hand. | The first cars were made by hand. |
Was は I、he、she、it と使い、were は we、you、they と使う。Past simple: was / were と同じ区別だ。
| 主語 | be動詞 | 過去分詞 | 例文 |
|---|---|---|---|
| I / he / she / it | was | built | It was built in 1920. |
| we / you / they | were | cancelled | The concerts were cancelled. |
過去分詞
過去分詞は、動詞の3つ目の形だ。現在完了形で have の後に使う形と同じものだ。
規則動詞は -ed を付けて過去分詞を作る。スペルの規則（短母音の後は語末の子音を重ねる：stop → stopped、無音の -e を省く：close → closed）も過去形と完全に同じだ。詳しくは Past simple: regular verbs を参照。
| 原形 | 過去形 | 過去分詞 |
|---|---|---|
| invite | invited | invited |
| close | closed | closed |
| paint | painted | painted |
不規則動詞は独自の過去分詞の形を持つ（不規則動詞表の第3列）。過去形と同じ場合もあれば、違う場合もある：
| 原形 | 過去形 | 過去分詞 |
|---|---|---|
| break | broke | broken |
| write | wrote | written |
| make | made | made |
| know | knew | known |
| steal | stole | stolen |
よく使う不規則動詞の一覧は Past simple: irregular verbs で確認できる。
行為者を示す（by + 行為者）
誰が動作を行ったか言いたいときは、文末に by + 行為者 を加える：
- The report was written by the director.
- This painting is admired by millions of visitors.
- The decision was made by the committee.
by 句は省略可能——行為者が重要または興味深い場合にのみ使う。不明または重要でない場合は省く。
否定文
Not は am / is / are / was / were の後に置く：
| 時制 | 形 | 例文 |
|---|---|---|
| 現在形 | am / is / are + not + 過去分詞 | It is not used any more. / It isn't used. |
| 過去形 | was / were + not + 過去分詞 | The window wasn't broken. / They were not invited. |
よく使う短縮形：isn't、aren't、wasn't、weren't。注意：am not は平叙文では標準的な短縮形がない——✅ I am not invited または I'm not invited、しかし ❌ I amn't invited。
日本語では「〜された」「〜られた」のように一語で受動を表せるが、英語の受動態では be動詞（am/is/are/was/were）+ 過去分詞 が必要だ。be動詞を省いて過去分詞だけにすることはできない。たとえば The window broken だけでは文として成り立たず、The window was broken としなければならない。
疑問文
疑問文では am / is / are / was / were が主語の前に来る：
| 時制 | 形 | 例文 |
|---|---|---|
| 現在形 | Am / Is / Are + 主語 + 過去分詞？ | Is this product sold online? Am I included? |
| 過去形 | Was / Were + 主語 + 過去分詞？ | Was the parcel delivered? |
短い答え方はbe動詞に合わせる：Yes, it is / No, it isn't; Yes, it was / No, it wasn't.
疑問詞を使う疑問文では、疑問詞が文頭に来る：
- Where is this coffee grown?
- When was the palace built?
- Who was the symphony composed by?（改まった表現：By whom was it composed?）
よくある間違い
- ❌ The window was break. → ✅ The window was broken. （過去分詞を使う。原形や過去形では誤り）
- ❌ Coffee is grew in Brazil. → ✅ Coffee is grown in Brazil. （不規則な過去分詞：grow → grown）
- ❌ The letters was delivered. → ✅ The letters were delivered. （letters は複数 → were）
- ❌ The form signed by the manager. → ✅ The form was signed by the manager. （受動態には助動詞 was/were が必要）
- ❌ The film was directed very well by. → ✅ The film was directed very well. （行為者なしで by だけ残すのは誤り）
- ❌ They were inviting to the party. → ✅ They were invited to the party. （受動態には過去分詞を使う。-ing 形ではない）
確認問題
能動か受動か？正しい形を入れよう。
- This museum ____ (open) in 1887.（past passive）
- Thousands of people ____ (visit) this museum every year.（present active）
- The original paintings ____ (restore) last year.（past passive）
- By whom ____ the Mona Lisa ____ (paint)?（past passive question）
答えを見る
- This museum was opened in 1887.
- Thousands of people visit this museum every year.
- The original paintings were restored last year.
- By whom was the Mona Lisa painted?（より自然な表現：Who was the Mona Lisa painted by?）
まとめ
- 受動態は焦点を行為者から動作や結果に移す。The letter was written は手紙に注目しており、誰が書いたかではない。
- 現在形の受動態： 主語 + am / is / are + 過去分詞 → It is made here.
- 過去形の受動態： 主語 + was / were + 過去分詞 → It was built in 1920.
- 規則動詞の過去分詞は過去形と同じ（closed、painted）。不規則動詞には独自の過去分詞形がある（broken、written、made）。
- Was は I / he / she / it と、were は we / you / they と使う。
- by + 行為者 は行為者が重要な場合のみ。不明または重要でなければ省く。
- 否定：isn't used、wasn't built、weren't invited。
- 疑問：be動詞を主語の前に移す → Was it built here? Is it used often?