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O 1

1. Used before the name of or a pronoun referring to a person or thing being formally addressed: "How can I put it to you, O you who prepare to travel with important matters on your mind?" (Jo Durden-Smith).
2. Used to express surprise or strong emotion: "O how I laugh when I think of my vague indefinite riches" (Henry David Thoreau).

O 2

The symbol for oxygen.

O 3

1. Sports
a. offense
b. offensive
2. office telephone number
3. Baseball out
4. outside
5. outstanding
6. Sports overtime


or O  (ō)
n. pl. o's or O's also os or Os
1. The 15th letter of the modern English alphabet.
2. Any of the speech sounds represented by the letter o.
3. The 15th in a series.
4. Something shaped like the letter O.
5. O One of the four major blood groups in the ABO system. Individuals with this blood group have neither A nor B antigens on the surface of their red blood cells, and have both anti-A and anti-B antibodies in their blood serum.
6. A zero.


(əʊ) or


n, pl o's, O's or Os
1. (Linguistics) the 15th letter and fourth vowel of the modern English alphabet
2. (Phonetics & Phonology) any of several speech sounds represented by this letter, in English as in code, pot, cow, move, or form
3. another name for nought


symbol for
1. (Elements & Compounds) chem oxygen
2. (Biochemistry) a human blood type of the ABO group. See universal donor
3. (Logic) logic a particular negative categorial proposition, such as some men are not married: often symbolized as SoP. Compare A, E, I2
abbreviation for
(General Sporting Terms) slang Austral offence
[(for sense 3) from Latin (neg)o I deny]


1. a variant spelling of oh
2. an exclamation introducing an invocation, entreaty, wish, etc: O God!; O for the wings of a dove!.

O, o


n., pl. O's Os, o's os oes.
1. the 15th letter of the English alphabet, a vowel.
2. any spoken sound represented by this letter.
3. something shaped like an O.
4. a written or printed representation of the letter O or o.



interj., n., pl. O's. interj.
1. (used before a name in direct address, esp. in solemn or poetic language, to lend earnestness to an appeal): Hear, O Israel!
2. (used as an expression of surprise, pain, annoyance, longing, gladness, etc.)
3. the exclamation “O.”
[1125–75; Middle English < Old French < Latin ō]


1. Old.
2. Gram. object.


1. the 15th in order or in a series.
2. the Arabic numeral; zero; cipher.
3. a major blood group. Compare ABO system.
4. oxygen.


(ə, ō),
1. of: o'clock; will-o'-the-wisp.
2. Chiefly Dial. on.
[Middle English; by shortening.]


a prefix meaning “descendant,” in Irish family names: O'Brien; O'Connor.
[representing Irish ó descendant, Old Irish au]


, Chem.


var. of ob- before m: omission.


var. of oo-: oidium.


the typical ending of the first element of compounds of Greek origin, used regularly in forming new compounds with elements of Greek origin and often used in English as a connective irrespective of etymology: Franco-Italian; geography; seriocomic; speedometer. Compare -i-.
[Middle English (< Old French) < Latin < Greek]


1. a suffix occurring as the final element in informal shortenings of nouns (ammo; combo; promo); -o also forms nouns, usu. derogatory, for persons or things exemplifying or associated with that specified by the base noun or adjective (pinko; weirdo; wino).
2. a suffix occurring in informal noun or adjective derivatives, usu. grammatically isolated, as in address: kiddo; neato; righto.


1. pint.
[< Latin octārius]
2. October.
3. Ohio.


1. ocean.
2. pint.
[< Latin octārius]
3. octavo.
4. off.
5. old.
6. only.
7. order.
8. out.


The symbol for oxygen.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.o - a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gasO - a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust
chemical element, element - any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter
liquid oxygen, LOX - a bluish translucent magnetic liquid obtained by compressing gaseous oxygen and then cooling it below its boiling point; used as an oxidizer in rocket propellants
air - a mixture of gases (especially oxygen) required for breathing; the stuff that the wind consists of; "air pollution"; "a smell of chemicals in the air"; "open a window and let in some air"; "I need some fresh air"
H2O, water - binary compound that occurs at room temperature as a clear colorless odorless tasteless liquid; freezes into ice below 0 degrees centigrade and boils above 100 degrees centigrade; widely used as a solvent
gas - a fluid in the gaseous state having neither independent shape nor volume and being able to expand indefinitely
ozone - a colorless gas (O3) soluble in alkalis and cold water; a strong oxidizing agent; can be produced by electric discharge in oxygen or by the action of ultraviolet radiation on oxygen in the stratosphere (where it acts as a screen for ultraviolet radiation)
2.o - the 15th letter of the Roman alphabet
Latin alphabet, Roman alphabet - the alphabet evolved by the ancient Romans which serves for writing most of the languages of western Europe
alphabetic character, letter of the alphabet, letter - the conventional characters of the alphabet used to represent speech; "his grandmother taught him his letters"
3.o - the blood group whose red cells carry neither the A nor B antigensO - the blood group whose red cells carry neither the A nor B antigens; "people with type O blood are universal donors"
blood group, blood type - human blood cells (usually just the red blood cells) that have the same antigens


o [əʊ]
A. N
1. (= letter) → O, o f
O for OliverO de Oviedo
2. (= number) (Telec etc) → cero m
B. EXCL (poet) → ¡oh!
C. CPD O Grade N (Scot) (Scol) (formerly) → bachillerato m elemental (examen oficial que se solía realizar en el cuarto curso de secundaria)
O level N (Brit) (Scol) (formerly) → bachillerato m elemental (examen oficial que se solía realizar en el cuarto curso de secundaria)


o [ˈəʊ]
(= letter) → O, o m
O for Oliver (British)O comme Oscar
O for Oboe (US)O comme Oscar
(US) (=outstanding) → tb(= très bien)
num (= zero) → zéro
O God, I want to go home → Oh mon Dieu, je veux rentrer la maison.
O how mistaken you are! → Oh comme tu te trompes!


(Poet) → o; O my peopleo du mein Volk!
(expressing feeling) → oh, ach; O how wrong he waswie hatte er sich da (doch) geirrt; O for a bit of fresh air!ach, wenn es doch nur ein bisschen frische Luft gäbe!; O to be in France(ach,) wäre ich nur in Frankreich! ? also oh


, o
O nt, → o nt
[(Brit)] [(US)] (Telec) → Null f


o [əʊ] n
a. (letter) → O, o f or m inv
O for Oliver (Am) O for Oboe → O come Otranto
b. (number) (Telec) → zero
c. (Am) (Scol) =outstandingottimo


o [əʊ] excl (liter) → oh!


(əu) interjection
an expression used when speaking to a person, thing etc.

see also oh.

ozone, O

n. agente poderoso, forma tóxica de oxígeno.