IMPERSONAL PRONOUN “ONE”
We use the pronouns “one” and “you” to express something referring to everyone in general.
You have to show your passport at the border.
One has to show their passport.
The pronoun “you” is used in colloquial speech, whereas “one” is more formal:
One must try to be happy.
A possessive adjective referring to pronoun “one” take over the form “one’s”.
One ought to spend more time with one’s family.
Pronoun “one” often replace the noun and helps to avoid unnecessary repetitions.
He has a black car and I have a red one.
I like these dresses, but they are quite expensive. The cheapest one is 40 pounds. In the first sentence “a red one = a red car”; in the second sentence “the cheapest one = the cheap”.
“One” replace a concrete noun to avoid repetition.
He has a black car and I have a red car.
I like these dresses, but they are quite expensive. The cheapest dress is 40 pounds.
The pronoun “one” preceded by an adjective is used along with article “a” (when talking about any person or thing) and “the” (when talking about a concrete person or thing):
Take this skirt. It’s lovely.
Yes, but I wanted a blue one.
Give me that book.
No, not that one. The smaller one.
When you refer to the plural noun you should use a pronoun “ones”.
Make a copy of that page for me and a few ones for the rest of the team.
(a few ones = a few copies)
Sometimes a personal pronoun “they” has an additional meaning.
“They” can refer to people in general:
They say too much salt is bad for your health.
“They” can also refer to concrete people making decisions, giving approvals, establishing regulations.
They arrested him on the next day.
(they = the police)
They are going to close this school soon.
(they = local authorities)