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
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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:
It offers a sports-themed way of approaching the topic, called GOALS, representing G: get ready; O: open the conversation; A: ask the question; L: listen and respond and S: support and signpost.
From BBC ● Sep. 9, 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
Up until the Big O, I’ve lived by that rule.
From The Wall Street Journal ● Aug. 7, 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
"What did you come up with, O Brainy One?" they called out.
From "The Witches" by Roald Dahl
Velella velella, commonly known as by-the-wind sailors and closely related to the Portuguese man o' war, have been spotted on beaches across Anglesey, Gwynedd and Tenby.
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
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
“Man!” he said, “but it made us afeard, for we expeckit that we should have to pay for it wi’ some rare piece o’ ill luck, so as to keep up the average.
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
Nearby, the all-girls camp Heart O' the Hills also faced flooding.
From BBC ● Jul. 6, 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
It is hence possible to employ crude cresol, which contains varying quantities of the o-, m-, and p-compounds, in the manufacture of these tanning matters.
From Synthetic Tannins by Georg Grasser
The text of the larger o- fuda is often accompanied by curious pictures or symbolic illustrations.
From In Ghostly Japan by Lafcadio Hearn
Of the three isomeric xylenes o- and m-xylene dissolve in concentrated, p-xylene in fuming sulphuric acid only.
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
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. 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
The P. malariae-like and P. o. wallikeri genomes were both annotated using the Companion tool42.
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
“God should bless the man o. Me I hope I will also meet a mentor when I graduate,” Chetachi 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 Judge David O. Carter issued a preliminary injunction, calling HUD’s action arbitrary and capricious.
From Los Angeles Times ● Sep. 4, 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
We watch Finway nibble, mouth opening in an O. Madge copies him and I make a fish face too.
From "Muffled" by Jennifer Gennari
The victory meant Maguire improved her career Solheim Cup record to nine wins, three defeats and one halved match, to give her the highest winning percentage o any European player that has played five matches.
From BBC ● Sep. 11, 2026
Allow me to sing, o Muse, of a recent dinner conversation about “The Odyssey.”
From Salon ● Aug. 2, 2026
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
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
Anyway, sometimes o makes the ow sound even when the w’s not there, like in note.
From Absolutely Almost by Lisa Graff
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
Does the olfactory exhilaration also enhance play-calling, amplifying one’s grasp of X’s and O’s?
From Los Angeles Times ● Jan. 12, 2026
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
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
There were many X’s and O’s at the end of it.
From "Code Talker: A Novel About the Navajo Marines of World War Two" by Joseph Bruchac
"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
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 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
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
Could it be that the screen can only fit 54 o’s at a time?
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
“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
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 Evan Evans
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
And from the shadow one by one Pick up the playful oes of sun?
From The Poetical Works of Robert Bridges by Robert Bridges
The poet "mouthing out his hollow oes and aes" is, we are told, a good description of Tennyson's tone and manner of reading.
From The Early Poems of Alfred Lord Tennyson by John Churton Collins
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.
