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• one
  one

  adjective

  being or amounting to a single unit or individual or entire thing, item, or object rather than two or more; a single.
• -one
  -one

  a suffix used in the names of ketones and analogous chemical compounds.
• –one
  –one

  A suffix used to form the names of chemical compounds containing an oxygen atom attached to a carbon atom, such as acetone.

one

¹ American  

[wuhn] / wʌn /

adjective

1. being or amounting to a single unit or individual or entire thing, item, or object rather than two or more; a single.

   one woman;

   one nation;

   one piece of cake.

2. being a person, thing, or individual instance or member of a number, kind, group, or category indicated.

   one member of the party.

3. existing, acting, or considered as a single unit, entity, or individual.

4. of the same or having a single kind, nature, or condition: We are of one resolve.

   We belong to one team.

   We are of one resolve.

5. noting some indefinite day or time in the future.

   You will see him one day.

6. a certain (often used in naming a person otherwise unknown or undescribed).

   One John Smith was chosen.

7. being a particular, unique, or only individual, item, or unit.

   I'm looking for the one adviser I can trust.

8. noting some indefinite day or time in the past.

   We all had dinner together one evening last week.

9. of no consequence as to the character, outcome, etc.; the same.

   It's all one to me whether they go or not.

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noun

• ones
  plural

1. the first and lowest whole number, being a cardinal number; unity.

2. a symbol of this number, as 1 or I.

3. a single person or thing.

   If only problems would come one at a time!

4. a die face or a domino face having one pip.

5. a one-dollar bill.

   to change a five-dollar bill for five ones.

6. Philosophy. One. (inNeoplatonism ) the ultimate reality, seen as a central source of being by whose emanations all entities, spiritual and corporeal, have their existence, the corporeal ones containing the fewest of the emanations.

pronoun

1. a person or thing of a number or kind indicated or understood.

   one of the Elizabethan poets.

2. (in certain pronominal combinations) a person unless definitely specified otherwise.

   every one.

3. (with a defining clause or other qualifying words) a person or a personified being or agency: the one I love.

   the evil one;

   the one I love.

4. any person indefinitely; anyone.

   One's score is never as good as one would desire.

5. Chiefly British. (used as a substitute for the pronoun I).

   Mother had been ailing for many months, and one should have realized it.

6. a person of the speaker's kind; such as the speaker's own self.

   to press one's own claims.

7. something or someone of the kind just mentioned: Your teachers this semester seem to be good ones.

   The portraits are fine ones.

   Your teachers this semester seem to be good ones.

8. something available or referred to, especially in the immediate area: The bar is open, so have one on me!

   Here, take one—they're delicious.

   The bar is open, so have one on me!

idioms

1. one by one, singly and successively.

   One by one the children married and moved away.

2. at one,

   1. in a state of agreement; of one opinion.

   2. united in thought or feeling; attuned.

      He felt at one with his Creator.

3. one and all, everyone.

   They came, one and all, to welcome him home.

4. one for the road. road.

-one ² American  

1. a suffix used in the names of ketones and analogous chemical compounds.

   lactone; quinone.

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-one ¹ British  

suffix

1. indicating that a chemical compound is a ketone

   acetone

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one ² British  

/ wʌn /

determiner

1. 1. single; lone; not two or more

      one car

   2. ( as pronoun )

      one is enough for now

      one at a time

   3. ( in combination )

      one-eyed

      one-legged

2. 1. distinct from all others; only; unique

      one girl in a million

   2. ( as pronoun )

      one of a kind

3. 1. a specified (person, item, etc) as distinct from another or others of its kind

      raise one hand and then the other

   2. ( as pronoun )

      which one is correct?

4. a certain, indefinite, or unspecified (time); some

   one day you'll be sorry

5. informal an emphatic word for a 1 an 1

   it was one hell of a fight

6. a certain (person)

   one Miss Jones was named

7. combined; united

8. 1. all the same

   2. of no consequence

      it's all one to me

9. (often foll by with) in a state of agreement or harmony

10. (of a man and a woman) to become married

11. many people

12. indefinite, undecided, or mixed

13. none

14. everyone, without exception

15. one at a time; individually

16. a few

17. on balance

18. informal exhibiting bad temper; ranting

19. on average

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pronoun

1. an indefinite person regarded as typical of every person

   one can't say any more than that

2. any indefinite person: used as the subject of a sentence to form an alternative grammatical construction to that of the passive voice

   one can catch fine trout in this stream

3. archaic an unspecified person

   one came to him

noun

1. the smallest whole number and the first cardinal number; unity See also number

2. a numeral (1, I, i, etc) representing this number

3. informal a joke or story (esp in the one about )

4. music the numeral 1 used as the lower figure in a time signature to indicate that the beat is measured in semibreves

5. something representing, represented by, or consisting of one unit

6. Also called: one o'clock.  one hour after noon or midnight

7. a blow or setback (esp in the phrase one in the eye for )

8. (in Neo-Platonic philosophy) the ultimate being

9. God

10. Satan; the devil

–one Scientific  

1. A suffix used to form the names of chemical compounds containing an oxygen atom attached to a carbon atom, such as acetone.

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one More Idioms  

More idioms and phrases containing one

• (one) picture is worth a thousand words
• A-1 (A-one)
• all in one piece
• all the same (one)
• as one
• at one
• at one stroke
• at one time
• at one time or another
• back to the drawing board (square one)
• each and every (last one)
• each other (one another)
• fast one
• for one, 1
• go one better
• hang (one) on
• harp on (one string)
• hole in one
• in one ear and out the other
• in the same (in one) breath
• irons in the fire, more than one
• it takes one to know one
• just one of those things
• look out for (number one)
• more than one way to skin a cat
• not one iota
• number one
• on the one hand
• put all one's eggs in one basket
• quick one
• seen one, seen them all
• six of one, half dozen of the other
• that's one on me
• tie one on
• wear another (more than one) hat
• with one arm tied behind one's back
• with one voice
• words of one syllable

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Grammar

One as an indefinite pronoun meaning “any person indefinitely, anyone” is more formal than you, which is also used as an indefinite pronoun with the same sense: One (or you ) should avoid misconceptions. One (or you ) can correct this fault in three ways. When the construction requires that the pronoun be repeated, either one or he or he or she is used; he or he or she is the more common in the United States: Wherever one looks, he (or he or she ) finds evidence of pollution. In speech or informal writing, a form of they sometimes occurs: Can one read this without having their emotions stirred? In constructions of the type one of those who (or that or which ), the antecedent of who is considered to be the plural noun or pronoun, correctly followed by a plural verb: He is one of those people who work for the government. Yet the feeling that one is the antecedent is so strong that a singular verb is commonly found in all types of writing: one of those people who works for the government. When one is preceded by only in such a construction, the singular verb is always used: the only one of her sons who visits her in the hospital. The substitution of one for I, a typically British use, is usually regarded as an affectation in the United States. See also he ¹, they.

Other Word Forms

Noun Inflected Forms

• ones
  plural

Etymology

Origin of one¹

First recorded before 900; Middle English oon, Old English ān; cognate with Dutch een, German ein, Gothic ains, Latin ūnus ( Old Latin oinos ); akin to Greek oínē “ace on a die”

Origin of -one²

Perhaps < Greek -ōnē feminine patronymic

Explanation

One refers to a single person or thing, as well as the number one. If you’re looking for a whole number between zero and two, you can only find one. One is all alone, but it at least it gets to be the first in line. It also gets to be the one and only, far and away the best, and one of a kind. If something (or someone) is "the one" you’ve been looking for, it’s exactly what you want. Sometimes one actually refers to more than one person being united in some way; if you and your friend are of "one mind," you think alike about something.

Example Sentences

See Examples For:

one -one –one ones

The list is overwhelmingly American with just one foreign-language film, Federico Fellini’s bittersweet 1953 comedy “I Vitelloni.”

From Los Angeles Times ● Aug. 21, 2026

Home with his mother before school, he was drafting a note to a teacher about a bad grade, and in between, he tapped out a few jokes and deleted each one.

From Slate ● Aug. 21, 2026

His lawyer said the ex-champion "need not prove one thing" and that he is "presumed innocent".

From BBC ● Aug. 21, 2026

Hardly one of his best-known films, “The Twelve Chairs” has proved one of the trickier titles for the Cinematheque to screen.

From Los Angeles Times ● Aug. 21, 2026

But one of the women in Joey’s group takes notice and calls Joey that night.

From "At Last She Stood" by Erin Entrada Kelly

A 13-day streak of temperatures being at 0C or below -one of the longest streaks for New York City since 1963 - ended on Friday after temperatures briefly tipped above 0C.

From BBC ● Feb. 9, 2026

The suffix, -one, changes the meaning to “large cake.”

From New York Times ● Dec. 20, 2021

The names for aldehyde and ketone compounds are derived using similar nomenclature rules as for alkanes and alcohols, and include the class-identifying suffixes -al and -one, respectively:

From Textbooks ● Feb. 14, 2019

Others thought they would never see the day that in conservative Idaho -one of the most Republican-dominated states in the nation- same-sex marriage would be legalized.

From Washington Times ● Dec. 28, 2014

Renn came after him, backing out on hands and knees and dragging two hazelwood packs -one of them his own.

From "Wolf Brother" by Michelle Paver

There are now two such vaccines –one made by Merck, another by Johnson & Johnson.

From The Guardian ● May 18, 2018

“Out of respect for Hayden’s loved ones and the ongoing investigation, there will be no further comment at this time.”

From Los Angeles Times ● Aug. 21, 2026

Participants therefore had to recognize that the associations had changed, learn the new ones, and respond with the correct button using the appropriate hand and finger.

From Science Daily ● Aug. 20, 2026

Matthew Upson: In the time Carrick was there, from January onwards, United showed they are definitely top-four material, and they are the ones I found it hardest to leave out.

From BBC ● Aug. 20, 2026

Its customers sign three-year contracts, leaving two years of obligations with no contracted revenue behind them, a gap it has to close by re-signing those customers or finding new ones.

From MarketWatch ● Aug. 20, 2026

And even though there were so many fewer letters after all except the first ones dropped out, the name felt bigger and freer.

From "Keeping Pace" by Laurie Morrison

Related Words

• anyone
• you