one3 S1 W1
used to emphasize a particular person or thing:
One person I find very difficult is Bob.
If there's one thing I can't stand, it's people who bite their nails.
on a particular day, morning etc in the past:
One morning I was sitting at my desk when a policeman knocked at my door.
used to talk about a day, morning etc in the future which is not yet exactly known or decided:
We should go out for a drink one evening.
One day she hopes to move to the South Coast.
used to talk about a particular person or thing in comparison with other similar people or things:
Why does my card work in one cash machine and not in another?
used to say that the second thing mentioned is very different from the first, and is often much more difficult to do:
It's one thing to say we have a goal; it's another to actually act on it.
used to introduce a reason for what you have just said:
He couldn't bring himself to say what he thought. For one thing, she seldom stopped to listen. For another, he doubted that he could make himself clear.
6 spoken especially American English
to be a very crazy woman, be a very interesting job etc:
You're one lucky guy.
used before the name of someone you do not know or have not heard of before [= a certain]:
He was accused of stealing a horse from one Peter Wright.