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
O's,
plural
Os,
plural
o's,
plural
os,
plural
oes
plural
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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:
Among those scheduled to perform are Beck, Jenny Lewis, Karen O, Rufus Wainwright and Devo, among many more.
From Los Angeles Times ● Jul. 8, 2026
God bless them for charming the good people of Boston and Miami and earning a full page feature in Wednesday's O Globo, Brazil's best-selling newspaper.
From BBC ● Jun. 25, 2026
“Our soul is in your hands, O Hussein!”
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
"What did you come up with, O Brainy One?" they called out.
From "The Witches" by Roald Dahl
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
The only signs of Violet are found on rocks - her Tam o' Shanter hat and a notebook recording road trips she had made to places including Sheffield and Edinburgh.
From BBC ● Sep. 23, 2024
“You a mate o’ young Jamie up the Big House, are ye?”
From "Code Name Verity" by Elizabeth Wein
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
Heart O' the Hills is another all-girls' camp that sits along the Guadalupe River, and it was right in the path of Friday's flood.
From BBC ● Jul. 5, 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
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 Grefé, Will
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
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
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
Gene models were then manually curated for both the P. malariae and P. o. curtisi reference genomes, using Artemis40 and the Artemis Comparison Tool41.
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
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
Crump said Thursday he was teaming up with Carl Douglas, a civil rights attorney known for representing O. J. Simpson during his 1995 murder trial, to explore a lawsuit against the county.
From Los Angeles Times ● Mar. 14, 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
Later that afternoon, Connie and I went into the bedroom to watch the O. J. Simpson verdict.
From "Tuesdays with Morrie" by Mitch Albom
"I never turn down a challenge. Stephanie Pineiro Aquino is a dangerous fighter, but nothing is going to stop me from getting my hand raised on April 4 in Cardiff. Yma o hyd."
From BBC ● Jan. 30, 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
Marvell and SoftBank didn’t immediately respond t o Barron’s requests for comment early on Thursday.
From Barron's ● Nov. 6, 2025
Including Henrietta. o n February 5, 1951, after Jones got Henriettas biopsy report back from the lab, he called and told her it was malignant.
From "The Immortal Life of Henrietta Lacks" by Rebecca Skloot
A bald-headed man it* Dragonwings o n perched on a stool behind a counter, his feet inside the rungs.
From "Dragonwings" by Laurence Yep
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
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
Since that press conference, other experts working for Letby's defence team have put forward another theory for Baby O's death.
From BBC ● Aug. 11, 2025
There has been another explanation for Baby O's death.
From BBC ● Aug. 11, 2025
“I know Coach O's got to be talking to you about playing football, too,” he continued.
From "Tradition" by Brendan Kiely
"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
On the personal side, Os is also relishing her relationship with Peso Pluma.
From Los Angeles Times ● Mar. 20, 2026
Criteria like this can be used to determine how likely it is that sequences of heads and tails or Xs and Os or hits and misses are randomly generated.
From "Innumeracy: Mathematical Illiteracy and Its Consequences" by John Allen Paulos
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
There is an envelope with my name, Hank Hooperman, in my mom’s curlicue handwriting with hearts above the o’s.
From "The Tenth Mistake of Hank Hooperman" by Gennifer Choldenko
Dreyfus pleased his friends no better than his :oes: he irked them by not becoming a "Dreyfusard."
From Time Magazine Archive
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 Collins, John Churton
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
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
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
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.
