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
O's,
plural
Os,
plural
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
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
-
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
-
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:
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
“Arise, O protector of the homeland!” the crowd responded.
From Los Angeles Times ● Jun. 22, 2026
Cuba has completely run out of diesel and fuel oil, the country's energy minister Vicente de la O Levy has said.
From BBC ● May 14, 2026
"And this change, O most learned Prince, has doubtless been brought to pass by the powerful incantations of those wicked persons who now call themselves kings and queens of Narnia."
From "The Horse and His Boy" by C.S. Lewis
Although their sting is generally considered "very mild" in comparison to Portuguese man o' war, Hobro advised people not to touch them.
From BBC ● Jun. 18, 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
Any way you slice it, this week’s Slate News Quiz is a piece o’ fun.
From Slate ● Nov. 1, 2024
And a horse named Upset handed the immortal Man o’ War his only loss in 22 races, earning the country’s oldest racetrack its nickname: the Graveyard of Champions.
From New York Times ● Jun. 7, 2024
Then he said quietly, “Thought o’ jus’ letting Buckbeak go...tryin ter make him fly away...but how d’yeh explain ter a hippogriff it’s gotta go inter hidin’?
From "Harry Potter And The Prisoner Of Azkaban" by J.K. Rowling
Visitor access to nearby Man O' War beach remains open.
From BBC ● Feb. 24, 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
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
Phenol-2,4-disulphonic acid is prepared from o- or p-phenolsulphonic acid, whereas phenol-2,4,6-trisulphonic acid is prepared directly from phenol by heating with concentrated sulphuric acid in presence of phosphorus pentoxide.
From Synthetic Tannins by Grasser, Georg
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
B-- -o-ey -o---- -o yo- -ro- old --ore le-- ---a-d --a- ---y --are -or -olle----- -or yo--o r--- --ll -all o- yo- ---r-day a- -o-r -e-.
From The Crevice by Grefé, Will
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
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
The Illumina-based genome assemblies for P. o. curtisi, P. o. wallikeri, and P. malariae-like were performed using MaSURCA30 for samples PocGH01, PowCR01, and PmlGA01 respectively.
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
“But sometimes one man can be both o. This is the season of weddings. When will it be my turn, Father Lord?”
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
On Saturday, we watched Bishop John O. Barres lay hands on Dillon’s head to confer the sacrament of the priesthood on him.
From The Wall Street Journal ● Jun. 22, 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
Crump said Thursday he was teaming up with Carl Douglas, a civil rights attorney known for representing O. J. Simpson during his 1995 murder trial, to explore a lawsuit against the county.
From Los Angeles Times ● Mar. 14, 2026
On this week’s show, Dahlia Lithwick interviews constitutional and immigration scholar Anna O. Law about her forthcoming book, Migration and the Origins of American Citizenship.
From Slate ● Mar. 14, 2026
He removed a wallet from his back pocket, demonstrating to O. J. Martinez that it was empty.
From "The Milagro Beanfield War" by John Nichols
Berkshire has the wherewithal of a huge stock buyback given that it’s sitting on o ver $350 billion of cash.
From Barron's ● Jan. 20, 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
The Red Dog Saloon, Más o Menos and the ad hoc gay bar Tiny Pony Tavern have found their footing for more ambitious desert nightlife.
From Los Angeles Times ● Jul. 21, 2025
According to the most recent count, at least 37 lawmakers have signed o nto the various resolutions.
From Salon ● Jun. 20, 2025
It’s her own medal of Saint Christopher—protector o travelers, guardian against storms, holy death, and toothaches.
From "A Heart in a Body in the World" by Deb Caletti
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
Certainly, I think given the amount of pastry I consume and have consumed in my lifetime, I thought that Mary O’s Irish Soda Bread scones were kind of a revelation.
From Los Angeles Times ● Oct. 3, 2025
Which raises the obvious question - if the prosecution were wrong about Baby O's liver injuries, then why did he die?
From BBC ● Aug. 11, 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
Kenia Os played up her cute and cuddly side in her previous album, 2024’s “Pink Aura” — but with her upcoming album “K de Karma,” out Friday, Os is putting that era to bed.
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
As a show of gratitude to the girls and the gays, Os transforms from “Belladona” to Primadonna in vogue-ready house bangers like “Slay,” “Problemática,” and “Boom In Your Face.”
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
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
Actual coaching — x’s and o’s — would become more important.
From New York Times ● Dec. 30, 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
Yr un peth a ellir ei ddywedyd am Daliesin Ben Beirdd, nid oes neb heddyw, hyd i gwn i, a fedr gyfieithu yn iawn un o’i Awdlau na’i Orchanau.
From Some Specimens of the Poetry of the Ancient Welsh Bards by Evans, Evan
Nad oes wedd na moes, masw ynyd yw’n gwlad, Nad oes mad eithr gwad a gwyd.
From Some Specimens of the Poetry of the Ancient Welsh Bards by Evans, Evan
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 Oliphant, Laurence
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
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
You could talk to him about os and argos, suet and grease, croteys, fewmets and fiants, but he only looked polite.
From "The Once and Future King" by T. H. White
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.
