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
-
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
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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:
Up until the Big O, I’ve lived by that rule.
From The Wall Street Journal ● Aug. 7, 2026
Bennett has reviewed one case, referred to in court as Baby O, in detail on behalf of her new defence.
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
There, buried under issues of O and Royalty Monthly, I find the booklet with its bright American flag waving on the cover.
From "A Place at the Table" by Saadia Faruqi and Laura Shovan
However, “in past El Niño events, we’ve seen similar-looking Portuguese man o’ war, a very rare visitor to our waters, washing up on our beaches.
From Los Angeles Times ● Jun. 15, 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
The witness was then asked about a line in another message, which the court heard said that Ms Wandelt recalled playing the playground game Ring a Ring o' Roses.
From BBC ● Oct. 9, 2025
Any way you slice it, this week’s Slate News Quiz is a piece o’ fun.
From Slate ● Nov. 1, 2024
See, the Ministry wanted ter send a bunch o’ Aurors, but Dumbledore said I’d do,” said Hagrid proudly, throwing out his chest and tucking his thumbs into his pockets.
From "Harry Potter and the Half-Blood Prince" by J.K. Rowling
Former basketball player Shaquille O’ Neal is also a high-profile investor.
From MarketWatch ● Nov. 19, 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
Girls summer camp Heart O’ the Hills is just a mile north of Camp Mystic.
From Salon ● Jul. 7, 2025
Heart O' the Hills wasn't in session and "most of those who were on camp at the time have been accounted for and are on high ground", the statement said.
From BBC ● Jul. 5, 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
Quintilianus saieth, that Ethopœia is a imitacion of o- ther meane maners: whom the Grekes dooe calle, not onelie Ethopœia, but mimesis, & this is in the maners, and the fact.
From A booke called the Foundacion of Rhetorike because all other partes of Rhetorike are grounded thereupon, euery parte sette forthe in an Oracion vpon questions, verie profitable to bee knowen and redde by Richard Rainolde
And trewelie, if there be any // and in no o- good in them, it is either lerned, borowed, or // ther tong. stolne, from some one of those worthie wittes of Athens.
From The Schoolmaster by Roger Ascham
Similarly, condensation of different samples of crude cresol containing varying quantities of o-, m-, and p-cresol did not yield end-products sufficiently different to justify describing them in detail.
From Synthetic Tannins by Georg Grasser
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 Georg Grasser
I don't think the "-e" should eliminate the existing "-o" and the "-a."
From Salon ● Sep. 26, 2022
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
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
The -o suffix traces back to old comic strip characters with names like Knocko and Groucho.
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
As a Gene Ontology database, the predicted Gene Ontology terms from the P. falciparum 3D7 genes orthologous to the P. malariae and P. o. curtisi genes included in the analysis were used.
From Nature ● Jan. 24, 2017
Using a new reference genome for P. malariae and a manually curated draft P. o. curtisi genome, we are now able to accurately place these species within the Plasmodium phylogeny.
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
Then she added, “Sorry o. I did not mean that your boyfriend is a criminal. I was just asking.”
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
The Senate opened debate this week on the late South Carolina senator’s legacy legislation—the Lindsey O. Graham Sanctioning Russia and Iran Act—by an overwhelming 86–12 vote.
From Slate ● Aug. 1, 2026
District Judge David O. Carter scheduled a hearing Friday to review it.
From Los Angeles Times ● May 7, 2026
News of diGenova’s appointment comes on the heels of a prosecutor withdrawing from the case, apparently due to doubts she had about prosecuting former CIA director John O. Brennan.
From Salon ● Apr. 21, 2026
With thirty-odd newspapers tucked under one strong arm, O. J. Martinez moved out on foot into the town’s narrow dirt roadways to deliver the news to Milagro.
From "The Milagro Beanfield War" by John Nichols
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
Welsh folk singer Dafydd Iwan says he has received "very personal" and "nasty" comments after urging organisers of a right-wing protest to stop using his song Yma o Hyd.
From BBC ● Feb. 1, 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
For example, shouldn’t is short for should not-, the apostrophe shows where the o in not was dropped.
From "Woe Is I" by Patricia T. O'Conner
Bennett relied on Baby O's neonatal notes as well as testimony from a police interview with the baby's mother about the infant's birth.
From BBC ● Jul. 22, 2026
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
Other experts, including the paediatric pathologist, said that Dr Aiton's observation of hyper-inflated lungs would not explain Baby O's liver injuries.
From BBC ● Aug. 11, 2025
The X’s and O’s won’t matter if Ayton doesn’t show up to play every night, however.
From Los Angeles Times ● Jul. 3, 2025
Coach O’s eyes followed him all the way into the locker room.
From "We'll Fly Away" by Bryan Bliss
"The Dutch experience in my opinion offers a warning for Canada," Os cautioned.
From BBC ● May 15, 2026
Os, born Kenia Guadalupe Flores Osuna in Mazatlán, Sinaloa, has made an incredible leap from social media influencer to Latin Grammy-nominated pop star in under a decade.
From Los Angeles Times ● Mar. 20, 2026
Os achieved an international breakthrough with her visual album, 2022’s “K23.”
From Los Angeles Times ● Mar. 20, 2026
Os would soon tour the U.S. for the first time, and at the 2023 Latin Grammy Awards, “K23” was nominated in the category of long form music video.
From Los Angeles Times ● Mar. 20, 2026
They were so surprised they both jumped, their arms went up in the air, and their eyes and their mouths turned into big Os.
From "Ida B" by Katherine Hannigan
Like other Romance languages, Spanish divides most endings of nouns into masculine o’s or feminine a’s.
From Washington Times ● Dec. 12, 2021
Twitter’s closed captioning wrote it out twice, with each ¡Gol! featuring 27 o’s.
From Slate ● Jun. 17, 2018
Texting and Millennials The phone holds a million x’s and o’s.
From Forbes ● Jun. 5, 2013
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
“Because, see, we’re in Spanish class with all the a's and o’s at the end, and Troy just comes up with this name, Ema, just like that, and boom, it stuck. You see?”
From "Shelter (Book One): A Mickey Bolitar Novel" by Harlan Coben
Dreyfus pleased his friends no better than his :oes: he irked them by not becoming a "Dreyfusard."
From Time Magazine Archive
Cymmrodedd fy llyw lluoedd beri, Nid oes rwyf eirioes, aer dyfysgu, Cymro yw haelryw o hil Beli hir, Yn herwydd i brofi.
From Some Specimens of the Poetry of the Ancient Welsh Bards by Evan Evans
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 Francis Bacon
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 Arthur Machen
Illi robur et oes triplex, of which I believe no weapons of any assailant could get the better.
From Stories By English Authors: Italy (Selected by Scribners) by Laurence Oliphant
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
Newton disliked infinitesimals, the little os in his fluxion equations that sometimes acted like zeros and sometimes like nonzero numbers.
From "Zero: The Biography of a Dangerous Idea" by Charles Seife
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.
