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
-
Os,
plural
-
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:
Up until the Big O, I’ve lived by that rule.
From The Wall Street Journal ● Aug. 7, 2026
The prosecution argued that Baby O was born in good condition and was stable for 48 hours before he suddenly collapsed.
From BBC ● Jul. 22, 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
“I am a suppliant at your knees, O Queen,” he said.
From "Mythology: Timeless Tales of Gods and Heroes" by Edith Hamilton
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
“I’ll ge’ bi’ o’ breakfast up to Mum now.”
From "Watership Down: A Novel" by Richard Adams
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 wasn't in session and "most of those who were on camp at the time have been accounted for and are on high ground", the statement said.
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
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
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
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
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
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
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
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
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
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
“Yes o. Are you the person that will marry me? Meanwhile I told Don I am going out with you, so make sure you don’t go anywhere that he might go.”
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
In “Journey to the Ants,” Bert Hölldobler and Edward O. Wilson unveil these astonishing “microwildernesses” as part of their long investigations into ants’ social lives.
From The Wall Street Journal ● Aug. 3, 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
Chloe O. Davis devised writhing choreography for the six dancers who supplied some movement, in contrast to the mostly static chorus.
From The Wall Street Journal ● Jul. 13, 2026
News of diGenova’s appointment comes on the heels of a prosecutor withdrawing from the case, apparently due to doubts she had about prosecuting former CIA director John O. Brennan.
From Salon ● Apr. 21, 2026
As I sit here in my Aeron chair, thinking E. O. Wilson thoughts.
From "Middlesex: A Novel" by Jeffrey Eugenides
Allow me to sing, o Muse, of a recent dinner conversation about “The Odyssey.”
From Salon ● Aug. 2, 2026
Similarly, in June 2023, Iwan, called on protesters to stop using Yma o Hyd in opposition to housing asylum seekers at the Stradey Park Hotel in Carmarthenshire.
From BBC ● Feb. 1, 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
“Actually the Salon. Wonder where the second o went.”
From "Burning Blue" by Paul Griffin
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
Other experts, including the paediatric pathologist, said that Dr Aiton's observation of hyper-inflated lungs would not explain Baby O's liver injuries.
From BBC ● Aug. 11, 2025
The X’s and O’s won’t matter if Ayton doesn’t show up to play every night, however.
From Los Angeles Times ● Jul. 3, 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
“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
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
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
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
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
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
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
Nad oes wedd na moes, masw ynyd yw’n gwlad, Nad oes mad eithr gwad a gwyd.
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
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.
