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.
being a person, thing, or individual instance or member of a number, kind, group, or category indicated: one member of the party.
existing, acting, or considered as a single unit, entity, or individual.
of the same or having a single kind, nature, or condition: We belong to one team.We are of one resolve.
noting some indefinite day or time in the future: You will see him one day.
a certain (often used in naming a person otherwise unknown or undescribed): One John Smith was chosen.
being a particular, unique, or only individual, item, or unit: I'm looking for the one adviser I can trust.
noting some indefinite day or time in the past: We all had dinner together one evening last week.
of no consequence as to the character, outcome, etc.; the same: It's all one to me whether they go or not.
the first and lowest whole number, being a cardinal number; unity.
a symbol of this number, as 1 or I.
a single person or thing: If only problems would come one at a time!
a die face or a domino face having one pip.
a one-dollar bill: to change a five-dollar bill for five ones.
One. Philosophy. (in Neoplatonism) 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.
a person or thing of a number or kind indicated or understood: one of the Elizabethan poets.
(in certain pronominal combinations) a person unless definitely specified otherwise: every one.
(with a defining clause or other qualifying words) a person or a personified being or agency: the evil one;the one I love.
any person indefinitely; anyone: One's score is never as good as one would desire.
Chiefly British. (used as a substitute for the pronoun I): Mother had been ailing for many months, and one should have realized it.
a person of the speaker's kind; such as the speaker's own self: to press one's own claims.
something or someone of the kind just mentioned: The portraits are fine ones.Your teachers this semester seem to be good ones.
something available or referred to, especially in the immediate area: Here, take one—they're delicious.The bar is open, so have one on me!
Idioms about one
one by one, singly and successively: One by one the children married and moved away.
one for the road. road (def. 10).
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 he1, they.
Other definitions for -one (2 of 2)
a suffix used in the names of ketones and analogous chemical compounds: lactone; quinone.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
How to use one in a sentence
Added to drinking water at concentrations of around one part per million, fluoride ions stick to dental plaque.
In his view, a writer has only one duty: to be present in his books.Houellebecq’s Incendiary Novel Imagines France With a Muslim President | Pierre Assouline | January 9, 2015 | THE DAILY BEAST
Yet this, in the end, is a book from which one emerges sad, gloomy, disenchanted, at least if we agree to take it seriously.Houellebecq’s Incendiary Novel Imagines France With a Muslim President | Pierre Assouline | January 9, 2015 | THE DAILY BEAST
The fear of violence should not determine what one does or does not say.
The al Qaeda-linked gunmen shot back, but only managed to injure one officer before they were taken out.
Practise gliding in the form of inflection, or slide, from one extreme of pitch to another.Expressive Voice Culture | Jessie Eldridge Southwick
He alludes to it as one of their evil customs and used by them to produce insensibility.Tobacco; Its History, Varieties, Culture, Manufacture and Commerce | E. R. Billings.
There was a rumor that Alessandro and his father had both died; but no one knew anything certainly.Ramona | Helen Hunt Jackson
Truth is a torch, but one of enormous size; so that we slink past it in rather a blinking fashion for fear it should burn us.Pearls of Thought | Maturin M. Ballou
Under the one-sixth they appear as slender, highly refractive fibers with double contour and, often, curled or split ends.A Manual of Clinical Diagnosis | James Campbell Todd
British Dictionary definitions for one (1 of 2)
single; lone; not two or more: one car
(as pronoun): one is enough for now; one at a time
(in combination): one-eyed; one-legged
distinct from all others; only; unique: one girl in a million
(as pronoun): one of a kind
a specified (person, item, etc) as distinct from another or others of its kind: raise one hand and then the other
(as pronoun): which one is correct?
a certain, indefinite, or unspecified (time); some: one day you'll be sorry
a certain (person): one Miss Jones was named
in one or all in one combined; united
all the same
of no consequence: it's all one to me
at one (often foll by with) in a state of agreement or harmony
be made one (of a man and a woman) to become married
many a one many people
neither one thing nor the other indefinite, undecided, or mixed
never a one none
one and all everyone, without exception
one by one one at a time; individually
one or two a few
one way and another on balance
off on one informal exhibiting bad temper; ranting
one with another on average
an indefinite person regarded as typical of every person: one can't say any more than that
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
archaic an unspecified person: one came to him
the smallest whole number and the first cardinal number; unity: See also number (def. 1)
a numeral (1, I, i, etc) representing this number
informal a joke or story (esp in the one about)
music the numeral 1 used as the lower figure in a time signature to indicate that the beat is measured in semibreves
something representing, represented by, or consisting of one unit
Also called: one o'clock one hour after noon or midnight
a blow or setback (esp in the phrase one in the eye for)
the one (in Neo-Platonic philosophy) the ultimate being
the Holy One or the One above God
the Evil One Satan; the devil
- Related prefixes: mono-, uni-
- Related adjective: single
British Dictionary definitions for -one (2 of 2)
indicating that a chemical compound is a ketone: acetone
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Scientific definitions for -one
A suffix used to form the names of chemical compounds containing an oxygen atom attached to a carbon atom, such as acetone.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Other Idioms and Phrases with one
In addition to the idioms beginning with one
- one and all
- one and only
- one and the same
- one another
- one by one
- one eye on
- one fell swoop, in
- one foot in the grave, have
- one for the books
- one for the road
- one good turn deserves another
- one in a million
- one jump ahead
- one man's meat is another man's poison
- one of a kind
- one of these days
- one of those days
- one on one
- one on, that's
- one picture is worth a thousand words
- one up
- one way or another
- all in one piece
- all the same (one)
- A-1 (A-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
- (one) picture is worth a thousand words
- 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
(Note that this listing does not include those idioms where one is a personal pronoun meaning “someone” or “oneself.”)
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.