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-.
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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:
“Arise, O protector of the homeland!” the crowd responded.
From Los Angeles Times ● Jun. 22, 2026
“We remain loyal to our promise, O Hussein!” they shouted.
From Los Angeles Times ● Jun. 22, 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
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
"O enlightened Vizier," said the Tisroc, "bestow your wisdom upon us concerning this strange proposal."
From "The Horse and His Boy" by C.S. Lewis
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
Any way you slice it, this week’s Slate News Quiz is a piece o’ fun.
From Slate ● Nov. 1, 2024
"She worked so hard, to get up at silly o' clock... and to wear corsets for hours on end," she said, adding that she continued working right up to the end of her life.
From BBC ● Sep. 28, 2024
But at the end o’ last year he began sending away loads of stuff, not only leaf.
From "The Return of the King" by J.R.R. Tolkien
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
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 Ascham, Roger
The text of the larger o- fuda is often accompanied by curious pictures or symbolic illustrations.
From In Ghostly Japan by Hearn, Lafcadio
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
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
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
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
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
“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
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
Mr. Yagoda is the author of the novel “Alias O. Henry.”
From The Wall Street Journal ● Apr. 17, 2026
Anna O. Law: The biggest myth about American immigration is that until the federal government started enforcing our borders in the late 19th century, it was just open borders.
From Slate ● Mar. 16, 2026
Scientists observed that the fungus parasitizes cells of O. cf. ovata and can kill them within a few days.
From Science Daily ● Mar. 6, 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
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
It calls on the US to "reassure the people of Palau" that civilians will be protected if conflict was o break out.
From BBC ● Nov. 23, 2025
Shares o Carvana were down 7.9% in after-hours trading following the release.
From Barron's ● Oct. 29, 2025
But I feel that in order to do our duty to the party, we gotta—” o o o .. which is why I ask it.
From "Feed" by M.T. Anderson
“Me and my madam and the children are leaving tomorrow morning for the village. I came to tell you to stay well. Ka o di.”
From "Half of a Yellow Sun" by Chimamanda Ngozi Adichie
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
Carson Palmer’s coaching staff, filled with former NFL players like himself, have shown they can teach, lead and handle X’s and O’s.
From Los Angeles Times ● Nov. 23, 2025
There has been another explanation for Baby O's death.
From BBC ● Aug. 11, 2025
Finally de la O’s dad landed a full-time job in a meat-packing factory in Saint Paul, Minnesota.
From "Boots on the Ground: America's War in Vietnam" by Elizabeth Partridge
"The Dutch experience in my opinion offers a warning for Canada," Os cautioned.
From BBC ● May 15, 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
Since then, Os has come to rule the Latin pop scene in Mexico, boasting multiple sold-out tours of the country.
From Los Angeles Times ● Mar. 20, 2026
“I want to grow more internationally with this album,” says Os.
From Los Angeles Times ● Mar. 20, 2026
Funny thing is I knew what the shirt said because of the two Os in the middle.
From "The Truth as Told by Mason Buttle" by Leslie Connor
They eventually named their institute for an online trend that had slime enthusiasts replacing the vowels in their name with double o’s, so Kira would become “Kooroo” and slime becomes “Sloomoo.”
From Washington Post ● Jun. 30, 2022
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
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
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
Dreig Arfon arfod wythlonedd Dragon diheufeirch heirddfeirch harddedd, Ni chaiff Sais i drais y droedfedd oi fro, Nid oes o Gymro i Gymrodedd.
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
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
In the 19 3 os, track experts were beginning to toss around the idea of a four-minute mile.
From "Unbroken" by Laura Hillenbrand
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
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
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.
