先行詞を修飾し、関係詞節の中からは重複をなくすために先行詞と同じ語が無くなる
（主文の詳細を関係代名詞で、あるいは名詞節で、説明できるようになる）
| 先行詞 | 主格 | 所有格 | 目的格 |
| 人 | who | whose | whom |
| 物/動物 | which | whose | which |
| 人・物・動物 | that | - | that |
| 先行詞を含む | what | - | what |
先行詞に最上級や序数詞、the only、the same、the very、every、allがついているときはthat
She is the most beautiful woman that I've ever seen.
前にwhoやwhichなどの疑問詞がくるとthat
Who is the lady that was here a few minutes ago?
前置詞が関係代名詞の前に出てくる場合がある
This is the hammer with which the boy broke the window (with).
whose/whom/of whichは複雑
That is the man whose wife is a senator.
The ledy whom you met at the ariport is the president.
She bought a table the surface of which was scratched.
Did you believe what he said?
whoever/whomever/whichever/whateverはwhatと同じで先行詞を含む
■関係副詞 - Relative adverb
where/when/why/howの4つ
前の3つは先行詞を省略することができて、その時は名詞節になる
しかしhowは先行詞を置かない
This is the place where the treaty was signed.
This is where the treaty was signed.
where = at whichみたいな
This is (the way) how Bill talks. howは先行詞を置かないのでthe wayが消える
how to の同格は避ける（先行詞を含む感覚が強いのだと思う）
こちらはOK： Provided a proposal for how to name the document.
名詞句で駄目： Provided a proposal how to name the document.
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■関係代名詞と関係副詞の違い
関係代名詞で接続する場合 This is the house which Susan was born in.
This is the house in which Susan was born.
関係副詞で接続する場合 This is the house where Susan was born.
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■節と句の違い
節はSVを含むが、句はSVを持たない
