基本の説明Overview
分詞構文は、when・because・as などの接続詞を使う代わりに、動詞の ing 形（または過去分詞）で始めて、2つの内容を短くつなぐ書き方です。「〜しながら」「〜なので」「〜したあとで」といった意味を、接続詞なしで表します。A participial phrase links two ideas briefly by starting with the verb's -ing form (or a past participle) instead of a conjunction such as when, because or as. It can mean “while”, “because”, “after” and so on, without any conjunction.
作り方は3ステップです。① 接続詞を消す。② 副詞節の主語が主節の主語と同じなら、その主語も消す。③ 動詞を ing 形にする。たとえば While I was walking along the street, I met an old friend. は、While と I was を消して Walking along the street, I met an old friend. になります。There are three steps. (1) Delete the conjunction. (2) If the subject of the subordinate clause is the same as the main subject, delete it too. (3) Change the verb to its -ing form. So While I was walking along the street, I met an old friend. becomes Walking along the street, I met an old friend.
接続詞がなくなるので、意味（時・理由など）は文脈から判断します。主に書き言葉で使われ、会話ではふつう接続詞を使った文のほうが多く使われます。Because the conjunction is gone, the meaning (time, reason, etc.) is judged from context. This form is used mainly in writing; in conversation, sentences with a conjunction are more common.
| 意味Meaning | もとの文（接続詞あり）Original (with conjunction) | 分詞構文Participial phrase |
|---|---|---|
| 時（〜するとき・〜して）Time (when / while) | When she opened the box, she found a letter. | Opening the box, she found a letter. |
| 理由（〜なので）Reason (because) | As I was tired, I went to bed early. | Being tired, I went to bed early. |
| 連続動作（そして〜）Sequence (and then) | He opened the window, and he let in fresh air. | He opened the window, letting in fresh air. |
| 付帯状況（〜しながら）Accompanying action (while) | She sat there, and she listened to music. | She sat there, listening to music. |
動詞のing形 〜, 主語 + 動詞 …. （＝ When[Because, As] 主語 + 動詞 〜, 主語 + 動詞 ….）verb-ing ~, subject + verb …. (= When[Because, As] subject + verb ~, subject + verb ….)否定は ing の前に not を置く（Not knowing 〜）。受け身の意味なら過去分詞（Written 〜）、主節より前のことなら Having + 過去分詞 を使う。For a negative, put not before -ing (Not knowing ~). For a passive meaning use a past participle (Written ~); for something earlier than the main verb use Having + past participle.
分詞構文の意味上の主語は、ふつう主節の主語と同じです。主語が違うときは、分詞の前に主語を残して The weather being fine, we went out.（天気がよかったので、私たちは出かけた）のように言います（やや堅い形です）。The understood subject of the participle is normally the same as the main subject. When the subjects differ, keep the subject before the participle: The weather being fine, we went out. (a rather formal form).
例文で確認Example sentences
① 時を表す（〜するとき・〜して）1. Time (“when / while”)
Walking along the street, I met an old friend.
通りを歩いていると、私は旧友に会いました。
= While I was walking along the street, I met an old friend.= While I was walking along the street, I met an old friend.
Opening the box, she found a letter.
箱を開けると、彼女は手紙を見つけました。
= When she opened the box, she found a letter.= When she opened the box, she found a letter.
Looking out of the window, Emi saw a rainbow.
窓の外を見て、エミは虹を見つけました。
Getting off the bus, Ken dropped his hat.
バスを降りるとき、ケンは帽子を落としました。
② 理由を表す（〜なので）2. Reason (“because”)
Feeling tired, she decided to go to bed early.
疲れを感じたので、彼女は早く寝ることにしました。
= Because she felt tired, she decided to go to bed early.= Because she felt tired, she decided to go to bed early.
Being sick, Tom stayed home.
具合が悪かったので、トムは家にいました。
Being は省略して Sick, Tom stayed home. と言うこともある。Being is sometimes left out: Sick, Tom stayed home.
Not knowing what to say, he stayed silent.
何を言えばよいかわからず、彼は黙っていました。
否定は ing の前に not。For a negative, put not before the -ing form.
Living near the school, Mika can walk there.
学校の近くに住んでいるので、ミカは歩いて通えます。
③ 受け身の意味（過去分詞で始める）3. Passive meaning (starting with a past participle)
Written in simple English, this book is easy to read.
やさしい英語で書かれているので、この本は読みやすいです。
Being written の Being が省略された形。Short for Being written, with Being left out.
Seen from the plane, the island looked very small.
飛行機から見ると、その島はとても小さく見えました。
= When it was seen from the plane, ...= When it was seen from the plane, ...
Born in Kyoto, she knows a lot about its history.
京都で生まれたので、彼女はその歴史にくわしいです。
Surprised at the news, Tom could not say a word.
その知らせに驚いて、トムは一言も言えませんでした。
④ 連続動作・付帯状況（〜しながら／そして〜）4. Sequence and accompanying action (“while / and”)
She sat on the sofa, listening to music.
彼女は音楽を聞きながらソファーに座っていました。
主節のあとに置くと「〜しながら」の意味になりやすい。After the main clause it usually means “while doing”.
He opened the window, letting fresh air into the room.
彼は窓を開けて、部屋に新鮮な空気を入れました。
Tom stood there, looking at the sky.
トムは空を見上げながらそこに立っていました。
He was sitting with his arms crossed.
彼は腕を組んで座っていました。
〈with + 名詞 + 分詞〉で「〜を…した状態で」。腕は「組まれる」側なので過去分詞。“with + noun + participle” means “with something in a certain state”. The arms are crossed, so a past participle.
⑤ 完了形の分詞構文（主節より前のこと）5. Perfect participial phrase (earlier than the main verb)
Having finished his homework, Ken went out to play.
宿題を終えてから、ケンは遊びに出かけました。
宿題を終えたのは、出かけるより前。そのため Having + 過去分詞 にする。He finished his homework before going out, so use Having + past participle.
Having lived in Canada for five years, she speaks English well.
カナダに5年間住んだことがあるので、彼女は英語が上手です。
Not having eaten anything since morning, I was very hungry.
朝から何も食べていなかったので、私はとてもおなかがすいていました。
否定形は Not having + 過去分詞。The negative is Not having + past participle.
⑥ 慣用的な分詞構文（決まった言い方）6. Fixed expressions
Generally speaking, Japanese summers are hot and humid.
一般的に言って、日本の夏は暑くて湿気が多いです。
主語に関係なく使える決まった表現。A set phrase that can be used regardless of the subject.
Judging from the dark clouds, it will rain soon.
暗い雲から判断すると、もうすぐ雨が降りそうです。
Speaking of sports, what do you like best?
スポーツの話といえば、何がいちばん好きですか。
確認クイズQuick check
下の文を分詞構文に直したり、（ ）内の動詞を正しい形に直したりして、空所を埋めましょう。Fill in each blank by rewriting the sentence as a participial phrase or by putting the verb in the right form.
- 次の文を分詞構文に直す：Rewrite as a participial phrase: While I was walking along the river, I found a wallet. → ___ along the river, I found a wallet.
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Walking — 接続詞 While と主語 I was を消して ing 形にする。Delete While and I was, and use the -ing form. - 次の文を分詞構文に直す：Rewrite as a participial phrase: Because he didn't know the way, he asked a policeman. → ___ the way, he asked a policeman.
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Not knowing — 否定は ing の前に not を置く。For a negative, put not before the -ing form. - 次の文を分詞構文に直す：Rewrite as a participial phrase: Because it was written in easy English, the book was popular. → ___ in easy English, the book was popular.
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Written — 「書かれた」という受け身の意味なので、過去分詞から始める（Being written の Being を省略）。The meaning is passive, so start with the past participle (Being written with Being omitted). - 次の文を分詞構文に直す：Rewrite as a participial phrase: After she had finished lunch, Emi went out. → ___ lunch, Emi went out.
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Having finished — 昼食を終えたのは出かけるより前なので Having + 過去分詞。She finished lunch before going out, so Having + past participle. - Tom sat on the bench, ___ (read) a magazine.
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reading — 「雑誌を読みながら」という付帯状況。ing 形にする。This is accompanying action (“while reading”), so use the -ing form. - ___ (see) from the hill, the town looks beautiful.
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Seen — 町は「見られる」側なので過去分詞。The town is seen by someone, so the past participle.
おさえておきたいポイントKey points
- 分詞構文は、接続詞 + 主語 + 動詞 の部分を、動詞の ing 形で始まる形に書きかえたものA participial phrase rewrites “conjunction + subject + verb” into a phrase that starts with verb-ing
- 意味（時・理由・連続動作・付帯状況など）は、前後の文脈から判断するThe meaning (time, reason, sequence, accompanying action, etc.) is judged from context
- ふつうは、分詞の意味上の主語と主節の主語が同じときに使うIt is normally used when the participle's subject is the same as the main subject
- 否定は Not -ing 〜、受け身の意味なら過去分詞から始めるThe negative is Not -ing ~; for a passive meaning, start with a past participle
- 主節より前のことは Having + 過去分詞 で表すUse Having + past participle for something that happened before the main verb
- Generally speaking や Judging from のような慣用表現は、決まった形で覚えるLearn fixed phrases such as Generally speaking and Judging from as they are
よくある間違いCommon mistake："Walking along the street, a dog bit me." ✗ → "Walking along the street, I was bitten by a dog." ✓ 歩いていたのは「私」なので、主節の主語を I にします。"Walking along the street, a dog bit me." ✗ → "Walking along the street, I was bitten by a dog." ✓ The one who was walking is “I”, so I must be the main subject.
よくある間違いCommon mistake："Knowing not what to say, he stayed silent." ✗ → "Not knowing what to say, he stayed silent." ✓ 否定の not は ing 形の前に置きます。"Knowing not what to say, he stayed silent." ✗ → "Not knowing what to say, he stayed silent." ✓ Put not before the -ing form.
よくある間違いCommon mistake："Writing in simple English, this book is easy to read." ✗ → "Written in simple English, this book is easy to read." ✓ 本は「書かれる」側なので過去分詞を使います。"Writing in simple English, this book is easy to read." ✗ → "Written in simple English, this book is easy to read." ✓ A book is written by someone, so use the past participle.