When we are talking about countable things, we can use one or ones if it is clear what we are talking about. We use one and ones as a substitute of a noun mentiones before. Here the word one and ones mean (artinya) “yang.” To avoid repeating yourself, you can use one or ones. But it has to be clear from the situation what you are talking about.
We use one is used to replace a singular countable noun.
– Which is your girl friend? The one with glasses?
– I like the hand phone. So, I take the silver one.
– I asked for a cup, but they did not have one.
The word ones is used to replace a plural countable noun.
– I broke my glasses so I will have to buy some new ones.
– These shoes on shelf are too expensive.
– You can buy the ones on the floor.
Which shirts do you like? The ones over there.
You have to specify 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.
Words like NEW or THESE specify which ones you mean.
If you do not specify which ones (i.e. you do not describe which ones with an adjective etc.), you should use SOME:
– I broke my glasses so I will have to buy SOME.
– I like those shoes. I think I will buy SOME.
We can use one with adjectives, but in that case we need to use a:
– I’d like to buy a house. If I can afford it, I’ll get a big one.
– A very important point about using “one” is that it is referring to an indefinite thing.
You cannot use “one” to replace a definite thing, like “the car” or “my bike”, or a proper noun, like something’s name (e.g. “Sony”).
– In the definite case, you need a pronoun, like “it”. Compare: “I need a pen. Do you have one?” and “The car broke down. I need to take it to the mechanic.”
Matthew. 2015. One and Ones to Replace Countable Nouns. Retrieved from: https://poligo.com/en/articles/grammar/one-and-ones-replace-countable-nouns
Riyanto, Slamet, et al. A Handbook of English Grammar, An Effective Way to Master English. Pustaka Pelajar.