❶（同じ種類のもののうちの）1つ; （～の）もの
✓POINT
前に出た普通ふつう名詞の代わりに使う. 複数形 ones は前に必ず the, 形容詞などがつき, 単独で ones を使うことはない.
Do you have a camera?—No, I don't, but my brother has one (=a camera). He will lend it (=the camera) to you.
会話Do you have a camera?—No, I don't, but my brother has one a camera. He will lend it the camera to you.
君はカメラを持っている?—いや持っていないけど兄が（1つ）持っている. 彼はそれ[そのカメラ]を君に貸してくれるだろう.
文法 ちょっとくわしく
one は前に出た名詞そのものでなく, それと同種類のものを指す. it は前に出た名詞そのものを指す.
Will you bring me that dictionary?—This one (=dictionary)?
会話Will you bring me that dictionary?—This one dictionary?
その辞書を私に持ってきてくれますか.—これですか.
Look! Bob and Ben are playing tennis.—Which one is Bob?
会話Look! Bob and Ben are playing tennis.—Which one is Bob?
ほら! ボブとベンがテニスをしている.—どっちがボブ?
I don't like this tie. Please show me a better one (=tie).
I don't like this tie. Please show me a better one tie.
このネクタイは気に入りません. もっといいのを見せてください.
⦣ 形容詞＋one の時は a, an, the などがつく.
These hats are nice, but I like the ones on the shelf better.
These hats are nice, but I like the ones on the shelf better.
これらの帽子ぼうしもいいけど, 私は棚たなの上にあるもののほうが好きだ.
I like these old shoes better than the new ones (=shoes).
I like these old shoes better than the new ones shoes.
私はこの古い靴くつのほうがその新しいのよりも好きだ.
Parent birds carry food to their young ones.
Parent birds carry food to their young ones.
親鳥たちがひな鳥に食べ物を運んで来る.
one after anotherone after another
one after the otherone after the other
one anotherone another
お互たがい
The lovers looked at one another.
The lovers looked at one another.
恋人こいびとたちはお互いを見つめ合った.
At Christmas we give presents to one another.
At Christmas we give presents to one another.
クリスマスには私たちはお互いにプレゼントを贈おくり合う.
one of these daysone of these days
one ～ the other ～one ～ the other ～
（2つのうち）1つは～もう1つは～, （2人のうち）1人は～もう1人は～
We have two dogs; one is white, and the other (is) black.
We have two dogs; one is white, and the other (is) black.
うちには犬が2匹ひきいて, 1匹は白でもう1匹は黒です.
A is one thing, B is another.A is one thing, B another.A is one thing, B (is) another.
A is one thing, B (is) another.
（A はある1つの事, そして B はまた別の事）A と B は別だ
To know is one thing, to teach another.
To know is one thing, to teach another.
知っているということと教えるということは別だ.
