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:
It also gives non-Asian chorus members a reason to be present at Butterfly’s wedding, though having a group of American ladies sing the invocation “O Kami! O Kami!” from song sheets seemed peculiar.
From The Wall Street Journal ● Aug. 17, 2026
Test your knowledge of the English language: How many words can you create with the letters P, Y, C, R, O, and T?
From Slate ● Jul. 20, 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
Rafferty was on a long list of musicians suggested by 69-year-old Frank O Reilly.
From BBC ● Jul. 15, 2026
Elizabeth’s eyes open wide, and her mouth stretches into an O as she figures out what I’m hinting at.
From "A Place at the Table" by Saadia Faruqi and Laura Shovan
Similar to Portuguese man o' war, by-the-wind sailors are colonies of animals related to sea anemones and corals, and they possess stinging cells.
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
“School gov’nors have bin told, o’ course,” said Hagrid miserably.
From "Harry Potter And The Prisoner Of Azkaban" by J.K. Rowling
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
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 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
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 soft, long-drawn "o- ohs!" that came to his ears were full of a music that made him impervious to pain.
From Green Fancy by George Barr McCutcheon
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
The P. malariae-like and P. o. wallikeri genomes were both annotated using the Companion tool42.
From Nature ● Jan. 24, 2017
Collated tables for all molecular evolution measures for all genes can be found in Source Data File 1 for P. malariae and P. o. curtisi.
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
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 elegantly presented “An Exquisite Eye: Introducing the Aso O. Tavitian Collection,” at the Clark, offers a preview with 150 works by artists from different countries, deploying different mediums, united by consistent excellence.
From The Wall Street Journal ● Aug. 29, 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
“E. O. Lawrence personally never quite demobilized after the end of World War II,” the Rad Lab physicist Wolfgang “Pief” Panofsky would observe many years later.
From "Big Science" by Michael Hiltzik
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
"The lack of justice has sparked this wave of protests," Abu Ahmed Faijul Kabir of the legal rights group Ain o Salish Kendra told AFP.
From Barron's ● May 22, 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
Other times, for the players who preferred to see plays spelled out with Xs and O’s, he’d diagram it on paper.
From Los Angeles Times ● Aug. 24, 2025
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
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
“I knows what them is,” he said, putting his finger on the X’s and O’s.
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
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
Kenia Os played up her cute and cuddly side in her previous album, 2024’s “Pink Aura” — but with her upcoming album “K de Karma,” out Friday, Os is putting that era to bed.
From Los Angeles Times ● Mar. 20, 2026
Os reveals that she and Morrison worked on a third song that they’re still putting the finishing touches on.
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
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
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
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
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 Arthur Machen
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
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.
