one and ones

When we are talking about countable things, we can use ONE or ONES if it is clear what we are talking about.

To avoid repeating yourself, you can use ONE when you are talking about a singular countable noun or ONES when you are talking about a plural countable noun. But it has to be clear from the situation what you are talking about.

• I asked for a glass, but they did not have one.
• I broke my glasses so I will have to buy some new ones.
• I like those shoes, but let's buy THESE ones.

With uncountable nouns we use SOME, ANY or nothing:

• I asked for beer, but they did not have any.
• If you need some more money, I can lend you some.
• Apple juice is cheap, but orange is expensive. (Nothing after 'orange')

You have to be specific about which ONES you mean. Check these examples:

• I broke my glasses so I will have to buy some NEW ones.
• I like those shoes, but let's buy THESE ones.
• My car is the red one.