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
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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:
The MAL story also illustrates how much complexity is hidden behind the familiar letters A, B, AB and O.
From Science Daily ● Sep. 19, 2026
A delicious word salad: How many words can you create with the letters Y, B, O, F, U, and N?
From Slate ● Aug. 18, 2026
“No doubt about it... You cannot understand the power of the O factor,” he said.
From Los Angeles Times ● Aug. 14, 2026
Up until the Big O, I’ve lived by that rule.
From The Wall Street Journal ● Aug. 7, 2026
It was by the finger-post at the end of the village, and I laid my hand upon it, and said, “Good-bye, O my dear, dear friend!”
From "Great Expectations" by Charles Dickens
“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
These sea snails are also voracious predators themselves and feast upon free-floating hydrozoan such as Velella velella and Portuguese man o’ war.
From Los Angeles Times ● Jul. 23, 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
It makes me ireful to think o’ them.
From "Dracula" by Bram Stoker
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
Sir Ringo can be heard narrating in the new footage alongside a slightly different bespoke musical arrangement by longtime series composer Mike O' Donnell.
From BBC ● May 9, 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
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 Will Grefé
The text of the larger o- fuda is often accompanied by curious pictures or symbolic illustrations.
From In Ghostly Japan by Lafcadio Hearn
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 Georg Grasser
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
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
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
The P. o. wallikeri and the P. o. curtisi chromosomes were aligned against each other, as were the P. malariae and P. malariae-like chromosomes.
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
“Haba! I don’t text and drive o. I text when I’m not driving,” she 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
District Court Judge David O. Carter ordered the VA to build about 2,500 units of temporary and permanent housing in addition to the 1,200 required in the earlier lawsuit.
From Los Angeles Times ● Sep. 11, 2026
Thankfully, Curry did not allow any eerie rumors to deter him from securing the home, which was originally built in 1922, having been designed by acclaimed architect Stiles O. Clements.
From MarketWatch ● Aug. 31, 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
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
R. O. Shipman was the group chaplain’s name.
From "Catch-22" by Joseph Heller
“LAHD is very excited about the opportunities ...t o produce more affordable housing and stabilize the city’s housing stock,” said Tiena Johnson Hall, the housing department’s general manager.
From Los Angeles Times ● Sep. 23, 2026
Allow me to sing, o Muse, of a recent dinner conversation about “The Odyssey.”
From Salon ● Aug. 2, 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
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
“Amaka, o gini? I don’t like that tone!”
From "Purple Hibiscus" by Chimamanda Ngozi Adichie
Barely a week after tying the knot with Taylor Swift in July, Kansas City Chiefs tight end Travis Kelce was back at work inside Johnny O’s Gymnasium in Florida.
From The Wall Street Journal ● Sep. 30, 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
However, a paediatric pathologist who was not involved in the case but has seen Baby O's post-mortem report, says it was "unlikely" Baby O's liver injuries were caused by impact - as the prosecution claims.
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
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
In 1988, he founded Luaka Bop, a record label whose influential compilations have introduced American audiences to lesser-known classics of world pop and psychedelia, such as Brazil’s Os Mutantes.
From The Wall Street Journal ● Oct. 9, 2026
"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
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
The Gs in her name looked like nibbled Os.
From "Inkheart" by Cornelia Funke
Like other Romance languages, Spanish divides most endings of nouns into masculine o’s or feminine a’s.
From Washington Times ● Dec. 12, 2021
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
A young executive named Mark Shapiro, now gone, pushed it as a way to broaden the network's appeal beyond "the hard x's and o's crowd."
From Slate ● Jun. 1, 2011
Since the censors’ Greek was even worse than Milton’s, they often made mistakes, lopping off endearments, x’s and o’s.
From "Middlesex: A Novel" by Jeffrey Eugenides
Dreyfus pleased his friends no better than his :oes: he irked them by not becoming a "Dreyfusard."
From Time Magazine Archive
Dywedir mai enw y gwas oedd Dafydd Hiraddug, ac iddo werthu ei hun i’r diafol, ac oherwydd hyny, ei fod yn alluog i gyflawni gweithredoedd anhygoel yn yr oes hon.
From Welsh Folk-Lore a Collection of the Folk-Tales and Legends of North Wales by Elias Owen
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
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 Evan Evans
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.
