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
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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
The fest will feature a star-studded, all-women lineup including Rodrigo, Chappell Roan, Mitski, Doechii and special guests Karen O, Sarah McLachlan and Stevie Nicks.
From Los Angeles Times ● Aug. 28, 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
“Your wish is my command, O Great Timdini.”
From "Shine!" by J.J. and Chris Grabenstein
Velella velella, commonly known as by-the-wind sailors and closely related to the Portuguese man o' war, have been spotted on St Bees beach in recent weeks.
From BBC ● Jul. 30, 2026
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
“It wasn’ easy, gettin’ Aragog’s body out o’ there, I can tell yeh — they usually eat their dead, see...
From "Harry Potter and the Half-Blood Prince" by J.K. Rowling
June O' Sullivan, who runs a chain of 42 London Early Years Foundation nurseries, said she was yet to see evidence of AI benefits in early years.
From BBC ● Mar. 12, 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
Girls summer camp Heart O’ the Hills is just a mile north of Camp Mystic.
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
Quintilianus saieth, that Ethopœia is a imitacion of o- ther meane maners: whom the Grekes dooe calle, not onelie Ethopœia, but mimesis, & this is in the maners, and the fact.
From A booke called the Foundacion of Rhetorike because all other partes of Rhetorike are grounded thereupon, euery parte sette forthe in an Oracion vpon questions, verie profitable to bee knowen and redde by Richard Rainolde
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
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
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
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
This gene family was recently named KELT7, and we confirm the 8 copies present in P. o. wallikeri, but show that P. o. curtisi has 9 copies, two of which are pseudogenes.
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
Then she added, “Sorry o. I did not mean that your boyfriend is a criminal. I was just asking.”
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
And every day I’d say, “It was O. K.,” which now also stood for Overwhelming Kalamity.
From "Ida B" by Katherine Hannigan
“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
But the legs that underpin the stool of Wall Street’s still-bullish forecasts, in the form of Fed rate cuts, slowing inflation pressures, and a resilient economy, have started o wobble.
From Barron's ● Mar. 19, 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
“Actually the Salon. Wonder where the second o went.”
From "Burning Blue" by Paul Griffin
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
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
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
Long minutes passed, then de la O’s radio crackled with static: it was the radio operator reporting back, hysterical.
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, 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
“It’s very beautiful to know that you have a partner that knows what you go through and that can give you advice from his experiences as well,” Os says.
From Los Angeles Times ● Mar. 20, 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
Black and red letters and crazy eyes inside the Os.
From "Brown Girl Dreaming" by Jacqueline Woodson
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
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
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
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
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 Evan Evans
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
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
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.
