We use one (singular) and ones (plural) to avoid unnecessary repetition.

See those two girls? Helen is the tall one and Jane is the short one.
Which is your car, the red one or the blue one?
My trousers are torn. I need some new ones.
See those two girls. Helen is the one on the left.
Let’s look at the photographs. The ones you took in Paris.

We often use them after Which ... in questions:

You can borrow a book. Which one do you want?
There are lots of books here. Which ones are yours?

Exercise

Section: 

Comments

Hi,
Sometimes I see sentences like: "One could do...", "One could see that the sky is blue". I would like to have some explanations about the use of "one" in this case.
Thanks in advance

Hello manpeace,

In these cases, 'one' is a gender-neural indefinite pronoun, a little bit like 'on' in French or 'man' in German. It's not so commonly used in informal speech, but obviously as you have seen, it it's still in use in some contexts.

All the best,
Kirk
The LearnEnglish Team 

Thanks very much!

Hello,

I wrote your example again without one and ones. Is it wrong do that?

---8<---

See those two girls? Helen is the tall [] and Jane is the short [].

Which is your car, the red [] or the blue []?

My trousers are torn. I need some new [].

See those two girls. Helen is the one on the left. [In this case I think I can't remove that]

Let’s look at the photographs. The ones you took in Paris. [In this case I think I can't remove that]

Thank You

Franz Vegetarian

Hello Franz,

You're right that you can't remove 'one/s' from the last two sentences. I'm afraid you can't remove it from the first two sentences, either.

All the best,
Kirk
The LearnEnglish Team

Hello,
In example 2 (Which is your car, the red one or the blue one?) can I say (Which is your car, the red or the blue?) or that is wrong?

Hello Ola Jamal,

Although you can hear some examples like this from time to time they are quite unusual and occur in very formal and/or literary use, and even there they are rare. We would generally say the sentence with 'one' rather than without.

 

Best wishes,

Peter

The LearnEnglish Team

I love it. The exercises are very helpful.

Good day everyone
This lessons are quite interesting and I am learning a lot especially through practical activities or exercises. I am suggesting from our tutor at least to give us long pieces of writings to improve our writing skills.

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