plural ones
1
: the number 1
one, two, three, four, …
2
US
: a one-dollar bill
I don't have any ones. Can you break a five?
3
: one o'clock
I'll be there at one.
4
: the first in a set or series
On day one of his diet, he cut out sweets.
She wears a size one.
1
: that person or thing
"I'll have an iced tea, please." "I'll have one, too."
Their dog died, but they plan to get another one.
"You should wear the blue one." "The one with the stripes?" "No, the other one."
I'd like to see the ring next to that one.
Which one did you like better?
He is the one who called the police.
Have you heard the one about [=the joke about] the priest and the rabbi?
That's one possible answer—but not the only one.
He had one too many at the bar last night. [=he had too many alcoholic drinks at the bar]
Note: This sense of one can be used in the plural form ones.
2
: someone or something that is a part of a particular group
—+ of
I met one of your friends at the party.
She is one of the best players on the team.
One of the puppies has a brown patch around its eye.
He'll come back one of these days. [=someday]
Don't worry—he's one of us. [=he is part of our group and can be trusted]
3
a
somewhat formal
: people in general : any person
One never knows [=(more commonly) you never know] what the weather will be.
It is now possible to buy just about anything from the privacy of one's [=(more commonly) your] own home.
b
British, old-fashioned
: I or we
I would like to read more, but one doesn't have the time.
1
always used before a noun
: having the value of 1
There is one minute left in the game.
I have a few one-dollar bills in my purse.
She is one year old.
2
always used before a noun
—used to refer to a single person or thing
There is one cookie left.
Let's take it one day at a time. [=let's not think or plan too far ahead]
My one [=only, sole] concern is for your safety.
We need to keep all the tools in one [=the same] place.
He was the one (and only) person she wanted to marry.
He caught the ball one-handed.
a one-parent [=single-parent] family
There is only/just one more thing to do.
I could not solve one or two [=a few] problems on the test.
Not one person knew the answer. [=no one knew the answer]
3
a
—used before a noun to indicate that someone or something is part of a group of similar people or things
She is one singer who I would like to see in concert.
early one morning
The Grand Canyon is one place I'd like to visit.
That's one possible solution.
I don't like being around him. For one thing, he smokes.
The one thing I hate most is being lied to.
It's one thing to understand the problem, but another thing to actually fix it.
b
chiefly US, informal
—used to emphasize a description
She is one tough lady. [=she's a tough lady]
That is one ugly dog.
That was one great party.
4
always used before a noun
: not known exactly : some
I'll see you again one day soon.
He'll come back one day.
At one time or another/other, the building was a school.
5
—used to indicate that two or more people or things are actually the same person or are the same kind of thing
The writer and her main character are one.
"Puma" and "cougar" are different names for one animal.
The writer and her main character are one and the same.
6
formal
—used before a name to indicate that you do not know the person specified
One Ms. Jones called this morning. [=a woman named Ms. Jones called this morning]
7
not used before a noun
: in agreement with each other
You and I are one on this issue.
Cite this Entry
“One.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/one. Accessed 18 Apr. 2026.
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