Grammar Rule in 30 Seconds
Defining clauses identify exactly who/what you mean; non-defining clauses just add extra details using commas.
- Defining: No commas, 'that' is okay, essential for meaning. Example: 'The car that I bought is red.'
- Non-Defining: Use commas, 'that' is NOT okay, extra info only. Example: 'My car, which is red, is fast.'
- Omission: In defining clauses, you can drop 'who/which/that' if it's the object. Example: 'The book (that) I read.'
Overview
The cat that is white is so moody と言ったら、それは 制限用法（defining relative clause） を使っています。なぜでしょう？ that is white という部分がないと、どっちの猫の話をしているのか分からないからです！では、その友達が1匹しか猫を飼っていないと想像してください。もし My cat, which is white, is so moody と言ったら、それは 非制限用法（non-defining relative clause） です。「猫が白い」という事実は、単なる付け足しの情報にすぎません。あなたはすでにそれがどの猫か知っています。友達の唯一の猫ですから！How This Grammar Works
The movie that we watched last night was awesome と言ったら、that we watched last night という節がレーザーポインターになります。私がどの映画のことを言っているのかを正確に伝えます。もしこれを取り除いて The movie was awesome とだけ言ったら、あなたは「どの映画のこと？6時間もNetflix観てたんだけど」と思うでしょう。Inception, which we watched last night, was awesome と言ったら、あなたはすでにその映画が『インセプション』であることを知っています。「昨夜それを観た」という事実は、ちょっとしたおまけの情報です。その付箋を剥がしても、Inception was awesome という文は完璧に意味が通じます。My girlfriend who lives in London is coming to visit は、他の都市にも彼女がいることを暗示してしまいます（危険な発言ですね！）。一方、My girlfriend, who lives in London, is coming to visit は、ただ1人の彼女がどこに住んでいるかを教えてくれているだけです。
Formation Pattern
the laptop, my boss）。
who か that（制限用法）、または who のみ（非制限用法）を使います。
which か that（制限用法）、または which のみ（非制限用法）を使います。
that はかなりの内弁慶だと覚えておいてください。制限用法にしか住み着きません。非制限用法には絶対に行きません。
I, you, we など）が続く場合、関係代名詞を完全に消し去ることができます（The phone [that] I bought）。非制限用法では、関係代名詞は必須です。パーティーを絶対に去らないVIPのような存在です。
When To Use It
I want the burger that has no onions（玉ねぎ抜きのバーガーが欲しい）と言うとき、その節は100%必要です。それがないと、ランダムなバーガーが届いて、ディナーが台無しになります。似たようなもののグループから1つを区別するときに使いましょう。レビューにも最適です: The hotel that we stayed at was trash（私たちが泊まったホテルはゴミだった）、あるいは技術的な不満: The update that I downloaded broke my phone（ダウンロードしたアップデートのせいでスマホが壊れた）。Sarah, who has ten years of experience in marketing, joined our team. という文を見かけるかもしれません。彼女がサラであることはすでに分かっています。彼女の経験は、彼女がいかに有能かを示す理由にすぎません。名詞がすでに特定されている場合（人名、特定の場所 Paris、唯一の関係 my mother など）に使います。有名人の噂話をするなら、Taylor Swift, who is currently on tour, just released a new album. と言うでしょう。テイラーが誰かはみんな知っています。ツアーの情報は「ちなみに」という程度のものです。
Common Mistakes
- カンマのドラマ: 非制限用法でカンマを忘れるのが一番多い間違いです。
My dad who is a doctor lives in Berlinと書くと、お父さんが複数いて、医者の方のお父さんについて話していることになります。よほど特殊な家庭環境でない限り、カンマが必要です:My dad, who is a doctor, lives in Berlin. - 「that」の罠: 非制限用法で
thatを使ってしまうこと。✗ Paris, that I love, is beautiful.とは言えません。マトリックスのバグのように聞こえます。代わりにwhichを使いましょう:✓ Paris, which I love, is beautiful. - 「who」の混乱: 時々、人に対して
whichを使う人がいます。絶対にダメです！✗ The guy which lives next doorは大間違いです。正しくは✓ The guy who lives next doorです。 - 二重主語: 節の後ろに余計な代名詞を足してしまうこと。
✗ The car that I bought it is fast.itは要りません！関係代名詞thatがすでに目的語の役割を果たしています。スリムにしましょう:✓ The car that I bought is fast. - 省略しすぎ: 非制限用法で関係代名詞を消そうとすること。
✗ My brother, lives in Tokyo, is a chef.その隙間を埋めるためにwhoが必要です:✓ My brother, who lives in Tokyo, is a chef.
Contrast With Similar Patterns
My friend, a professional gamer, is rich。これは My friend, who is a professional gamer, is rich と非常によく似ています。違いは、関係代名詞節は動詞（is）を使うのに対し、同格は名詞句だけを使う点です。どちらも「追加情報」のために使われ、どちらもカンマが大好きです。The girl who is sitting over there と言う代わりに、単に The girl sitting over there と言うことができます。これは、より上級で「かっこいい」話し方で、ネイティブのように聞こえます。これは、関係代名詞が主語である制限用法のときだけ使えます。I know what you did「君がしたことを知っている」）。関係代名詞節は名詞を詳しく説明します（例: I know the person who did it「それをした人を知っている」）。一方は「何」について、もう一方は「誰」についてです。秘密を知っていることと、その秘密を話した人を知っていることの違いのようなものです。Quick FAQ
制限用法で which を使ってもいいですか？
はい、大丈夫です！ The car which I bought は完全に正しいですが、日常会話では that の方が一般的です。ただし、非制限用法では絶対に that を使わないでください。
who や that は省略してもいいですか？
制限用法で、かつその後に別の主語がある場合のみ可能です。 The man [who] I saw は OK です。 The man who saw me はダメです。ここでは who が主語なので必要です。
なぜ名前にカンマが必要なのですか？
名前ですでにその人が特定されているからです。 John と言えば、ジョンだと分かります。その後の情報は自動的に「追加」になるので、カンマが必要です。
これで文章のトーンは変わりますか？
全く変わります。非制限用法を使うと、より詳細で洗練された印象になります。制限用法は、単刀直入で明快な印象を与えます。これらを正しく使い分けることで、「初級」英語を卒業したことを示せます。
もし姉が2人いたら？
スペインに住んでいる方の姉について話したいなら、 My sister who lives in Spain と言いましょう。カンマなしです！これで聞き手は、あなたが2人のうちの1人を選んで話していることが分かります。魔法みたいでしょう？
Relative Pronoun Selection
| Function | For People | For Things | For Places/Time |
|---|---|---|---|
|
Subject
|
who / that
|
which / that
|
N/A
|
|
Object
|
who / whom / that / (ø)
|
which / that / (ø)
|
where / when
|
|
Possessive
|
whose
|
whose / of which
|
N/A
|
Pronoun Omission (Defining Only)
| Full Form | Short Form (Omitted) | Condition |
|---|---|---|
|
The man who I met
|
The man I met
|
Pronoun is the Object
|
|
The book that you read
|
The book you read
|
Pronoun is the Object
|
|
The man who lives here
|
NOT POSSIBLE
|
Pronoun is the Subject
|
Meanings
Relative clauses provide more information about a noun. Defining clauses limit the noun to a specific one, while non-defining clauses provide supplementary details about a noun already identified.
Defining (Restrictive)
Tells us which specific person or thing we are talking about. Without it, the sentence is incomplete or unclear.
“The students who studied hard passed the exam.”
“I'm looking for the keys that I left on the table.”
Non-Defining (Non-Restrictive)
Adds extra information about a noun we already know. The sentence still makes sense if you remove this clause.
“My brother, who lives in New York, is a chef.”
“The Eiffel Tower, which was built in 1889, is in Paris.”
Object Pronoun Omission
In defining clauses, if the relative pronoun is the object of the verb, it can be deleted.
“The movie (that) we watched was boring.”
“The person (who) I called didn't answer.”
Reference Table
| 特徴 | 限定用法 (Defining Clause) | 非限定用法 (Non-Defining Clause) |
|---|---|---|
|
目的
|
名詞を特定する
|
追加情報を提供する
|
|
カンマ
|
カンマは使わない
|
常にカンマを使う
|
|
'that'を使えるか？
|
はい（非常によく使う）
|
いいえ（絶対に使わない！）
|
|
関係代名詞を省略できるか？
|
はい（目的語の場合）
|
いいえ（絶対できない）
|
|
例
|
The car that I like...
|
My car, which I like,...
|
|
節を取り除いた場合の意味
|
文が不明瞭になる
|
文は依然として明確
|
フォーマル度スペクトル
The colleague with whom I collaborated on the project is absent. (Workplace)
The colleague who I worked with on the project is away. (Workplace)
The guy I worked with is out. (Workplace)
My project partner's ghosting today. (Workplace)
関係代名詞：特定テスト
限定用法（必須情報）
- カンマなし 特定
- thatを使う カジュアル／日常
非限定用法（追加情報）
- カンマあり おまけ情報
- thatは使わない 厳格なルール
限定用法 vs. 非限定用法
カンマは必要？不要？
その節を取り除いても文は意味が通じますか？
その名詞は固有名詞や唯一のもの（例：「パリ」）ですか？
関係代名詞の使い分け
どちらでも使える
- • Who (人に対して)
- • Which (物に対して)
- • Whose
- • Where
限定用法のみ
- • That
- • 省略（関係代名詞なし）
レベル別の例文
The boy who is happy is my brother.
The boy who is happy is my brother.
I have a dog that is big.
I have a dog that is big.
This is the book that I want.
This is the book that I want.
The girl who lives here is nice.
The girl who lives here is nice.
The car which he bought is blue.
The car which he bought is blue.
The man (who) I saw yesterday was tall.
The man (who) I saw yesterday was tall.
I like the city where I was born.
I like the city where I was born.
She is the teacher who helps me.
She is the teacher who helps me.
My sister, who lives in Rome, is a lawyer.
My sister, who lives in Rome, is a lawyer.
The laptop that I use for work is broken.
The laptop that I use for work is broken.
London, which is the capital of the UK, is huge.
London, which is the capital of the UK, is huge.
The man whose car was stolen is very angry.
The man whose car was stolen is very angry.
The company, which was founded in 1920, is closing.
The company, which was founded in 1920, is closing.
He failed his driving test, which was a surprise.
He failed his driving test, which was a surprise.
The candidate for whom I voted didn't win.
The candidate for whom I voted didn't win.
Is that the reason why you were late?
Is that the reason why you were late?
The building, the roof of which was damaged, is old.
The building, the roof of which was damaged, is old.
Anyone wishing to leave early may do so.
Anyone wishing to leave early may do so.
The method by which they achieved this is unknown.
The method by which they achieved this is unknown.
The town, where many artists live, is very vibrant.
The town, where many artists live, is very vibrant.
The project, the success of which remains to be seen, is costly.
The project, the success of which remains to be seen, is costly.
He was late, as is often the case with him.
He was late, as is often the case with him.
Whosoever finds the key shall be rewarded.
Whosoever finds the key shall be rewarded.
The situation, albeit difficult, is not hopeless.
The situation, albeit difficult, is not hopeless.
間違えやすい
Learners often use them interchangeably in all contexts.
Learners aren't sure when to use the object form 'whom'.
Both describe nouns but use different structures.
よくある間違い
The man which lives here.
The man who lives here.
I like the book what you gave me.
I like the book that you gave me.
The girl she lives next door is nice.
The girl who lives next door is nice.
I saw the man who he is a doctor.
I saw the man who is a doctor.
The house that I live is small.
The house where I live is small.
This is the man who's car is red.
This is the man whose car is red.
The movie who I saw was good.
The movie that I saw was good.
My mother, that is 50, is a nurse.
My mother, who is 50, is a nurse.
Paris which is in France is beautiful.
Paris, which is in France, is beautiful.
The man, who I met him, was nice.
The man, who I met, was nice.
The car, that's engine is broken, is mine.
The car, whose engine is broken, is mine.
文型パターン
The ___ who ___ is ___.
___, which is ___, is ___.
The ___ (that) I ___ was ___.
The person whose ___ is ___.
Real World Usage
My bestie, who is literally the cutest, just graduated!
I am looking for a role that allows me to use my coding skills.
The suspect, who was arrested late last night, is being questioned.
Did you find the keys I lost?
The theory, which was first proposed in 1990, remains controversial.
Take the train that goes toward the city center.
指差しトリック
カンマの後に「that」はNG
フォーマルさの違い
Smart Tips
Always use a non-defining clause with commas. Proper nouns are already specific, so any extra info is just 'extra'.
Use 'whom' after prepositions like 'to', 'with', or 'for'.
Check if there is another subject immediately after it. If there is, you can usually delete it.
Use ', which' at the end of the sentence.
発音
The Comma Pause
In non-defining clauses, there is a slight drop in pitch and a brief pause where the commas are.
Relative Pronoun Reduction
In fast speech, 'that' is often pronounced with a schwa /ðət/.
Non-defining Parenthetical
My car, (which is red), is fast.
The pitch goes down for the clause and back up for the main verb.
暗記しよう
記憶術
Defining is 'Determining' (no commas needed), Non-defining is 'Needless' (needs commas).
視覚的連想
Imagine a defining clause as a wedding ring—it's essential and stays on the finger. Imagine a non-defining clause as a bracelet—it's extra, and you can take it off (the commas are the clasps).
Rhyme
If it's extra, use a comma. If it's needed, save the drama.
Story
A detective is looking for 'the man who stole the diamond' (Defining). Once he catches him, he says, 'This man, who is wearing a red hat, is the thief' (Non-defining).
Word Web
チャレンジ
Look at 5 objects in your room. Write one defining and one non-defining sentence for each.
文化メモ
British speakers are slightly more likely to use 'which' in defining clauses than American speakers, who strictly prefer 'that'.
Using 'whom' is almost exclusively reserved for formal writing or very formal speeches. Using it in casual conversation can sound pretentious.
In some dialects, 'that' is used for people more frequently than 'who' in informal speech.
Relative pronouns in English evolved from demonstrative and interrogative pronouns in Old English ('se', 'seo', 'þæt').
会話のきっかけ
Tell me about a person who has influenced your life.
Describe your hometown, which I've never visited.
What's a movie that you've seen more than three times?
Think of a famous person whom you admire.
日記のテーマ
よくある間違い
Test Yourself
正しい文を選んでください:
Tokyo, ___ is the capital of Japan, is a huge city.
Find and fix the mistake:
Mr. Smith that is my teacher is very kind.
Score: /3
練習問題
8 exercisesMy brother, ___ lives in Spain, is visiting next week.
The woman ___ car was stolen called the police.
Find and fix the mistake:
The laptop, that I bought yesterday, is very fast.
I have a friend. He speaks five languages.
Match types
The cake that I ate was delicious.
The man who lives here is nice.
This is the park ___ we first met.
Score: /8
Practice Bank
10 exercisesThe phone ___ I bought yesterday is broken.
正しいのはどれですか？
Paris / is / which / beautiful / I / visited / , / ,
The girl which lives next door is nice.
Kucing yang sedang tidur itu milikku.
項目を一致させてください:
My mother, ___ is 60, still runs marathons.
特定のものを特定する文はどれですか？
The man who is standing there is my uncle.
The company, ___ headquarters are in London, is hiring.
Score: /10
よくある質問 (8)
Use a comma if the information is 'extra'. If the sentence still makes sense without it, add commas. If the info is needed to know which noun you mean, no commas.
In defining clauses, yes (e.g., 'The man that I saw'). In non-defining clauses, no—you must use 'who'.
'Who' is for subjects (the person doing the action). 'Whom' is for objects (the person receiving the action). 'Whom' is mostly used in formal writing.
No. You can only drop it in defining clauses when it is the object of the sentence (e.g., 'The book I read'). You cannot drop it if it is the subject (e.g., 'The book that is on the table').
In defining clauses, 'which' can sound slightly more formal than 'that', especially in British English. In non-defining clauses, 'which' is the only option for things.
Yes! It is perfectly natural to say 'The car whose engine is broken' instead of the more clunky 'The car the engine of which is broken'.
This is a standard rule of English grammar. 'That' is considered a restrictive pronoun, meaning its job is to limit or define. Non-defining clauses don't limit, so 'that' doesn't fit.
It might change the meaning! 'My brother who is a doctor' implies you have multiple brothers and you're talking about the doctor one. 'My brother, who is a doctor,' implies you have one brother and he happens to be a doctor.
Scaffolded Practice
1
2
3
4
Mastery Progress
Needs Practice
Improving
Strong
Mastered
In Other Languages
que / quien / el cual
English distinguishes between 'that' and 'which' based on commas; Spanish uses 'que' for both.
qui / que / lequel
French relative pronouns are determined by grammatical function (subject/object), not by the 'essentialness' of the info.
der / die / das
German requires commas for every relative clause, whereas English only uses them for non-defining ones.
Pre-nominal modifiers
Japanese uses word order (clause + noun) instead of pronouns (noun + who/which).
al-ladhi (الذي)
Arabic requires a pronoun like 'him' or 'it' inside the clause (e.g., 'the man who I saw him').
de (的)
Chinese places the description before the noun, while English places it after.
Learning Path
Prerequisites
Learn These First
関連動画
Related Grammar Rules
関係副詞：場所を表す 'Where'
Overview 素晴らしいピザ屋について友達に話そうとして、文の途中で詰まったことはありませんか？そう、あの店です。生地に蜂蜜...
形式的な関係詞節 (in which, to whom)
### Overview 洗練された英語の文章の核心をなす、フォーマルな関係節。これは、`preposition + which` または `preposition +...
文を短くする：短縮関係代名詞節
### Overview 英語学習において、中級から上級（B2レベル）へとステップアップする際、避けて通れないのが「文の洗練」です。こ...
Whose: 所有を示す
### Overview 英語の学習において、関係代名詞の `whose` は、文をスマートに繋ぎ、情報を凝縮させるための非常に強力なツール...
短縮関係節：分詞の使用（後置修飾）
### Overview 英語学習において、C2レベル、すなわち「熟達した」段階に到達するためには、単に文法的に正しい文章を書くだけで...
