O
noun
the fifteenth letter of the English alphabet, a vowel.
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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-.
-
-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 ).
-
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
-
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:
“Arise, O protector of the homeland!” the crowd responded.
From Los Angeles Times ● Jun. 22, 2026
“Coach O understands my expectations and commitment to being a championship program,” Kiffin said.
From Los Angeles Times ● May 21, 2026
Since January, only one shipment of Russian crude has reached Cuban ports, and the fuel refined from it has already been used, De la O said.
From The Wall Street Journal ● May 14, 2026
She was also nominated for an Oscar for "O... Saya", from the Slumdog Millionaire soundtrack.
From BBC ● May 5, 2026
Her mouth made a small O, like she was drinking from an invisible straw.
From "Maybe He Just Likes You" by Barbara Dee
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
Amelie McCann said Julia Wandelt had told her she had memories of playing Ring a Ring o' Roses with her and feeding her brother Sean.
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
“Not you. I’m fear’d you have some ill plans agate, that bring you about folk’s houses at this time o’ night.
From "Jane Eyre" by Charlotte Brontë
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
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
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
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 Grasser, Georg
The text of the larger o- fuda is often accompanied by curious pictures or symbolic illustrations.
From In Ghostly Japan by Hearn, Lafcadio
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
The soft, long-drawn "o- ohs!" that came to his ears were full of a music that made him impervious to pain.
From Green Fancy by McCutcheon, George Barr
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 P. malariae-like and P. o. wallikeri genomes were both annotated using the Companion tool42.
From Nature ● Jan. 24, 2017
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
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
“Me, I want as many governors as possible to come to my own wedding o. It shows levels, serious levels,” Ranyinudo said.
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
The one here involves the eight pits that were unearthed 40 years ago by workers in Sanxingdui in southern China “at the foot of the Tibetan mountains,” as narrator Jay O. Sanders tells us.
From The Wall Street Journal ● May 26, 2026
“It is not the trial of O. J. Simpson, the man accused of murdering my son and Nicole.”
From Los Angeles Times ● May 19, 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
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
“This company is the second largest taxpayer in the state of California and as such contributes very largely to the funds of the university,” he lectured Berkeley’s research dean, A. O. Leuschner.
From "Big Science" by Michael Hiltzik
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
Similarly, in June 2023, Iwan, called on protesters to stop using Yma o Hyd in opposition to housing asylum seekers at the Stradey Park Hotel in Carmarthenshire.
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
Shares o Carvana were down 7.9% in after-hours trading following the release.
From Barron's ● Oct. 29, 2025
One million helices stacked side by side would fit in this letter: o.
From "The Gene" by Siddhartha Mukherjee
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 times, for the players who preferred to see plays spelled out with Xs and O’s, he’d diagram it on paper.
From Los Angeles Times ● Aug. 24, 2025
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 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
But before he spoke he picked up a piece of yellow chalk and drew five X’s and O’s up on the board.
From "The Great Santini" by Pat Conroy
"The Dutch experience in my opinion offers a warning for Canada," Os cautioned.
From BBC ● May 15, 2026
On the personal side, Os is also relishing her relationship with Peso Pluma.
From Los Angeles Times ● Mar. 20, 2026
Os reveals that she and Morrison worked on a third song that they’re still putting the finishing touches on.
From Los Angeles Times ● Mar. 20, 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
“The rest, eh, Pip?” said Joe, looking at it with a slow, searching eye, “One, two, three. Why, here’s three Js, and three Os, and three J-O, Joes in it, Pip!”
From "Great Expectations" by Charles Dickens
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
Plosives, or stops, convey “slower” and “bigger” — as do vowels that are voiced at the back of the throat, like the o in “token” or the double o’s in “food.”
From New York Times ● Jan. 15, 2015
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 Cranes Conquer America was written at the top in Emily’s eight-year-old scrawl, back when she was into putting smiley faces inside her e’s, o’s, and o’s.
From "Book Scavenger" by Jennifer Chambliss Bertman
Dreyfus pleased his friends no better than his :oes: he irked them by not becoming a "Dreyfusard."
From Time Magazine Archive
And from the shadow one by one Pick up the playful oes of sun?
From The Poetical Works of Robert Bridges by Bridges, Robert
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
The os in his calculations were only intermediaries, crutches that vanished miraculously by the end of the computation.
From "Zero: The Biography of a Dangerous Idea" by Charles Seife
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
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.
