O
noun
the fifteenth letter of the English alphabet, a vowel.
Jump To:
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O
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o'
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O'
O'a prefix meaning “descendant,” in Irish family names.
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o-
o-an abridgment of ortho-.
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-o
-oa suffix occurring as the final element in informal shortenings of nouns (ammo; combo; condo; limo; promo ); -o also forms nouns, usually derogatory, for persons or things exemplifying or associated with that specified by the base noun or adjective (cheapo; pinko; sicko; weirdo; wino ).
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o.
o.abbreviationpint.
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-o-
-o-the typical ending of the first element of compounds of Greek origin (as -i- is, in compounds of Latin origin), used regularly in forming new compounds with elements of Greek origin and often used in English as a connective irrespective of etymology.
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O.
O.abbreviation(in prescriptions) a pint.
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o
onounthe 15th letter and fourth vowel of the modern English alphabet
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O'-
O'-prefix(in surnames of Irish Gaelic origin) descendant of
O
1 American
[oh]
/ oʊ /
Or
o
noun
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O's,
plural
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Os,
plural
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o's,
plural
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os,
plural
-
oes
plural
-
the fifteenth letter of the English alphabet, a vowel.
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any spoken sound represented by the letter O or o, as in box, note, short, or love .
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something having the shape of an O .
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a written or printed representation of the letter O or o.
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a device, as a printer's type, for reproducing the letter O or o.
O
2
American
[oh]
/ oʊ /
interjection
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(used before a name in direct address, especially in solemn or poetic language, to lend earnestness to an appeal).
Hear, O Israel!
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(used as an expression of surprise, pain, annoyance, longing, gladness, etc.)
noun
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O's
plural
O
3
American
O
4
American
Symbol.
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the fifteenth in order or in a series.
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the Arabic cipher; zero.
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(sometimes lowercase) the medieval Roman numeral for 11.
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Physiology. a major blood group, usually enabling a person whose blood is of this type to donate blood to persons of group O, A, B, or AB and to receive blood from persons of group O.
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Chemistry. oxygen.
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Logic. particular negative.
o'
5
American
[uh, oh]
/ ə, oʊ /
O'
6
American
o-
7
American
Chemistry.
o-
8
American
o-
9
American
-o
10
American
-
a suffix occurring as the final element in informal shortenings of nouns (ammo; combo; condo; limo; promo ); -o also forms nouns, usually derogatory, for persons or things exemplifying or associated with that specified by the base noun or adjective (cheapo; pinko; sicko; weirdo; wino ).
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a suffix occurring in colloquial noun or adjective derivatives, usually grammatically isolated, as in address.
cheerio; kiddo; neato; righto.
o.
11
American
abbreviation
o.
12
American
abbreviation
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octavo.
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off.
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old.
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only.
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order.
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Baseball. out; outs.
-o-
13
American
O.
14
American
abbreviation
O.
15
American
abbreviation
-
Ocean.
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octavo.
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October.
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Ohio.
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Old.
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Ontario.
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Oregon.
O
1
British
symbol
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chem oxygen
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a human blood type of the ABO group See universal donor
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logic a particular negative categorial proposition, such as some men are not married: often symbolized as SoP Compare A E I 2
abbreviation
o
2
British
/ əʊ /
noun
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the 15th letter and fourth vowel of the modern English alphabet
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any of several speech sounds represented by this letter, in English as in code, pot, cow, move, or form
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another name for nought
O
3
British
/ əʊ /
interjection
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a variant spelling of oh
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an exclamation introducing an invocation, entreaty, wish, etc
O God!
O for the wings of a dove!
O'-
4
British
prefix
-o
5
British
suffix
-o-
6
British
o-
7
British
prefix
o'
8
British
/ ə /
preposition
Other Word Forms
Noun Inflected Forms
Etymology
Origin of O2
First recorded in 1125–75; Middle English, from Old French, from Latin ō
Origin of o'5
From Middle English; by shortening
Origin of O'6
Representing Irish ó descendant, Old Irish au
Origin of -o10
Perhaps originally the interjection O, appended to words as in -o def. 2; as a derivational suffix reinforced by clipped forms of words with -o- as a linking element (e.g., photo, stereo ), by Rom nouns ending in o, and by personal nouns such as bimbo and bozo, of obscure origin
Origin of o.11
From the Latin word octārius
Origin of -o-13
Middle English (< Old French ) < Latin < Greek
Origin of O.14
From the Latin word octārius
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
In response, Evans said Baby O was born in good condition.
From BBC ● Jul. 22, 2026
Test your knowledge of the English language: How many words can you create with the letters P, Y, C, R, O, and T?
From Slate ● Jul. 20, 2026
The exhibition "Hkeeli ya Jnoub", or "Tell me, O South", features pictures and videos preserving the memory of southern Lebanon at the capital's Beit Beirut museum.
From Barron's ● Jul. 19, 2026
“We remain loyal to our promise, O Hussein!” they shouted.
From Los Angeles Times ● Jun. 22, 2026
O dear good faithful tender Joe, I feel the loving tremble of your hand upon my arm, as solemnly this day as if it had been the rustle of an angel’s wing!
From "Great Expectations" by Charles Dickens
Velella velella, commonly known as by-the-wind sailors and closely related to the Portuguese man o' war, have been spotted on St Bees beach in recent weeks.
From BBC ● Jul. 30, 2026
“Coffee badging”—going to the office just long enough to show your face and grab a cup o’ joe—was a popular workaround.
From The Wall Street Journal ● Dec. 30, 2025
I was raised about two blocks from where you lived at the time, near Tail o’ the Pup.
From Los Angeles Times ● Jan. 22, 2025
Any way you slice it, this week’s Slate News Quiz is a piece o’ fun.
From Slate ● Nov. 1, 2024
Not a lot o’ room on the seat with me on it, though, so you’ll be in the sidecar.”
From "Harry Potter and the Deathly Hallows" by J.K. Rowling
Former Nasa administrator Sean O' Keefe told the BBC that the nations that land on the Moon will have the advantage of exploring and developing the resources that are there.
From BBC ● Mar. 31, 2026
Former basketball player Shaquille O’ Neal is also a high-profile investor.
From MarketWatch ● Nov. 19, 2025
Girls summer camp Heart O’ the Hills is just a mile north of Camp Mystic.
From Salon ● Jul. 7, 2025
But Heart O’ the Hills confirmed that its camp director, Jane Ragsdale, is one of the flood’s victims .
From Salon ● Jul. 7, 2025
After a single trip to the supermarket, the refrigerator and the cupboards fill with familiar labels: Skippy, Hood, Bumble Bee, Land O’ Lakes.
From "The Namesake" by Jhumpa Lahiri
At week's end a Russian delegation got the signatures of the leaders of Kazakhstan on a similar agreement-to-try-t o- agree.
From Time Magazine Archive
Toluene treated with fuming sulphuric acid first yields o- and p-sulphonic acids, finally o- and p-disulphonic acids, ethylbenzene at the boiling point p-ethylbenzene-sulphonic acid.
From Synthetic Tannins by Grasser, Georg
Of the three isomeric xylenes o- and m-xylene dissolve in concentrated, p-xylene in fuming sulphuric acid only.
From Synthetic Tannins by Grasser, Georg
It is hence possible to employ crude cresol, which contains varying quantities of the o-, m-, and p-compounds, in the manufacture of these tanning matters.
From Synthetic Tannins by Grasser, Georg
In the absence of free sulphuric acid the conversion of o- into p-phenolsulphonic acid is brought about by heating the aqueous solution.
From Synthetic Tannins by Grasser, Georg
Usually words ending in "-o" are masculine and those ending in "-a" are feminine, but there are many common words that break those gender rules, like "la mano," the word for "hand."
From Salon ● Sep. 26, 2022
I don't think the "-e" should eliminate the existing "-o" and the "-a."
From Salon ● Sep. 26, 2022
The -o suffix traces back to old comic strip characters with names like Knocko and Groucho.
From Slate ● Mar. 31, 2020
Knocko, Peddlo, Henpecko, and the rest became so popular that the -o suffix soon spread to words up and down the English language.
From Slate ● Mar. 31, 2020
I knew perfectly well why, but I didn’t know how -o put it.
From "Boy: Tales of a Childhood" by Roald Dahl
Collated tables for all molecular evolution measures for all genes can be found in Source Data File 1 for P. malariae and P. o. curtisi.
From Nature ● Jan. 24, 2017
Gene models were then manually curated for both the P. malariae and P. o. curtisi reference genomes, using Artemis40 and the Artemis Comparison Tool41.
From Nature ● Jan. 24, 2017
Reality is that you are giving up your family time by doing the o. t. when they need you at work.
From Time ● May 3, 2013
“If you dey come give am ticket to leave this here country, I will disappear o. I will not even stop home for pick my bag.”
From Washington Post
“Yes o. Are you the person that will marry me? Meanwhile I told Don I am going out with you, so make sure you don’t go anywhere that he might go.”
From "Americanah" by Chimamanda Ngozi Adichie
Thus masc. -o- stems show palatal modification, e.g. corn, “horn,” plur. cyrn < *kornī; the plural ending of -u- stems, O. Gaulish -oves, gives O.W. -ou, Mid.
From Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 5 "Cat" to "Celt" by Various
In “Journey to the Ants,” Bert Hölldobler and Edward O. Wilson unveil these astonishing “microwildernesses” as part of their long investigations into ants’ social lives.
From The Wall Street Journal ● Aug. 3, 2026
And if he’s going to be a senator, he says, he needs to lock down a Jackie O. – not a Marilyn.
From Salon ● Jul. 6, 2026
After that came actress-comedian Imogene Coca’s silly, charismatic 1936 screen test for David O. Selznick, followed by Selznick’s home movies.
From The Wall Street Journal ● Jun. 10, 2026
Corona Centennial upset Corona 5-2 on Monday behind a complete game and 10 strikeouts from sophomore pitcher Christian De La O. Michael Nonis had three hits.
From Los Angeles Times ● Apr. 13, 2026
One time he blacked out all but the salutation “Dear Mary” from a letter, and at the bottom he wrote, “I yearn for you tragically. R. O. Shipman, Chaplain, U.S. Army.”
From "Catch-22" by Joseph Heller
My eyes watered as the camera panned over his arm-in-arm players as they shouted the line, “Think, o beloved homeland! That heaven/gave you a soldier in each son.”
From Los Angeles Times ● Jun. 25, 2026
Mr. Brownlee’s tenor proved rock-solid in Arturo’s demanding music, from his exquisitely relaxed, almost languid opening aria, “A te, o cara,” to some punishing high Fs.
From The Wall Street Journal ● Jan. 2, 2026
Marvell and SoftBank didn’t immediately respond t o Barron’s requests for comment early on Thursday.
From Barron's ● Nov. 6, 2025
According to the most recent count, at least 37 lawmakers have signed o nto the various resolutions.
From Salon ● Jun. 20, 2025
C is pronounced like k before a, o, u; and like s before e, i, y, and the diphthongs æ and œ: as cado, pronounced ka'do; cedo, pronounced se'do.
From New Word-Analysis by William Swinton
While some winning coaches were making their names with toughness that bordered on abuse, he urged Close to see her teams as human beings first, not X’s and O’s.
From The Wall Street Journal ● Apr. 6, 2026
Both senior managers were subsequently disciplined by Google for witnessing Mr O's conduct and failing to intervene, before later being made redundant.
From BBC ● Mar. 10, 2026
Does the olfactory exhilaration also enhance play-calling, amplifying one’s grasp of X’s and O’s?
From Los Angeles Times ● Jan. 12, 2026
The prosecution pathologist concluded that there was no evidence that a needle had pierced Baby O's liver while he was alive and the paediatric pathologist we spoke to agrees.
From BBC ● Aug. 11, 2025
When Elizebeth and her team stacked up the twenty-eight Enigma messages they had in December 1942, they discovered that the first column had far more O’s in it than anything else.
From "The Woman All Spies Fear" by Amy Butler Greenfield
"The Dutch experience in my opinion offers a warning for Canada," Os cautioned.
From BBC ● May 15, 2026
Another hurdle that Os had to overcome in her career is an ongoing stigma placed on influencers-turned-pop stars.
From Los Angeles Times ● Mar. 20, 2026
When Os first launched as a singer in 2018, some immediately took aim at her dance moves and the digitally augmented sound of her voice.
From Los Angeles Times ● Mar. 20, 2026
“It’s very beautiful to know that you have a partner that knows what you go through and that can give you advice from his experiences as well,” Os says.
From Los Angeles Times ● Mar. 20, 2026
He and George had the same thought at once, and their eyes went wide and their mouths formed Os of surprise and admiration.
From "Two Degrees" by Alan Gratz
Like other Romance languages, Spanish divides most endings of nouns into masculine o’s or feminine a’s.
From Washington Times ● Dec. 12, 2021
Speaking in the same New Orleans twang as her students—those bouncy o’s and long, lingering a’s—Foster was teaching her fifth-graders about chemical reactions.
From Slate ● Jun. 5, 2016
Mathematics said that any concept could be conveyed in such a binary code as long as the sequence of i’s and o’s was long enough.
From Forbes ● Sep. 2, 2014
The promotion is “a really great fit with an Americana brand,” Mr. Addicks said, particularly because “Cheerios have always been about nurturing; they’re the little o’s that go with you through life.”
From New York Times ● Nov. 9, 2011
It was almost perfect, just a fraction flatter and shakier than Betty Jean’s voice had been, the o’s and ah’s parodies of Betty Jean’s pretentious ones.
From "Jacob Have I Loved" by Katherine Paterson
Dreyfus pleased his friends no better than his :oes: he irked them by not becoming a "Dreyfusard."
From Time Magazine Archive
The colors that show best by candle-light are white, carnation, and a kind of sea-water-green; and oes, or spangs, as they are of no great cost, so they are of most glory.
From The Essays of Francis Bacon by Bacon, Francis
Ir wyfi yn meddwl nad oes neb a ryfygei gymmeryd y fath orchest arno.
From Some Specimens of the Poetry of the Ancient Welsh Bards by Evans, Evan
And from the shadow one by one Pick up the playful oes of sun?
From The Poetical Works of Robert Bridges by Bridges, Robert
I was taking a lesson in Welsh pronunciation some time ago, and uttered the phrase "yn oes oesodd"—from ages to ages.
From Far Off Things by Machen, Arthur
A new Longevity Preparedness Index from John Hancock and MIT AgeLab os based on a survey of over 1,300 adults and focused on eight areas such as finance, home, health and community.
From MarketWatch ● Dec. 12, 2025
She first broke through with 2016’s “Remonta,” an album she recorded with her former band Liniker e os Caramelows.
From Los Angeles Times ● Oct. 8, 2025
Ambos os programas são “fundamentais para entender a expansão agrícola no Brasil e as emissões de carbono do desmatamento na Amazônia,” diz Douglas Morton, especialista em sensoriamento remoto do Goddard Space Flight Center da NASA.
From Science Magazine ● May 26, 2022
Hours later, Kelly posts bail and os released from jail in Chicago.
From Seattle Times ● Aug. 18, 2021
In the 19 3 os, track experts were beginning to toss around the idea of a four-minute mile.
From "Unbroken" by Laura Hillenbrand
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
