one, ones

One replaces a countable noun in the singular. Ones replaces it in the plural. Use them when it is clear which noun you mean.

With an adjective

After an adjective you need one or ones. The adjective can't stand alone.

This one, that one, which one

One often follows this, that, which, the other and the … that/who.

Not with uncountable nouns

One and ones only replace nouns you can count. With uncountable nouns (milk, bread, water), leave the noun out or say it again.

Common mistakes

• × I like the red. (about a shirt) → I like the red one.
• × I want the new. → I want the new one.
• × These are the old one. → These are the old ones.
• × I don't have a pen. Can you lend me it? → Can you lend me one?
• × I'd like some milk. A cold one. → I'd like some cold milk.