o
1 of 11noun (1)
ˈō 
plural o's or os ˈōz
often capitalized, often attributive
1
a
: the 15th letter of the English alphabet
b
: a graphic representation of this letter
c
: a speech counterpart of orthographic o
2
: a graphic device for reproducing the letter o
3
: one designated o especially as the 15th in order or class
4
: something shaped like the letter O
especially : zero
o
2 of 11abbreviation (1)
1
ocean
2
ohm
3
old
4
order
5
over
O
3 of 11interjection
less common spelling of oh
1
—used to express an emotion (such as surprise or desire) or in response to physical stimuli
Oh, no! I forgot my key.Oh, don't stop!
2
—used in direct address
oh, waiter! Will you come here, please?
3
—used to express acknowledgment or understanding of a statement
Oh, yes. It's one of my favorite cities.
4
—used to introduce an example or approximation
Their house is about, oh, I'd say four miles from here.
O
4 of 11noun (2)
ˈō
: the one of the four ABO blood groups characterized by the absence of antigens designated by the letters A and B and by the presence of antibodies against these antigens
O
5 of 11abbreviation (2)
1
offense
2
Ohio
3
[New Latin octarius] pint
O
6 of 11symbol
oxygen
o-
7 of 11combining form
variants or oo-
: egg
oology
specifically : ovum
oogonium
o-
8 of 11abbreviation (3)
orth- or ortho-
-o-
9 of 11affix
—used as a connective vowel originally to join word elements of Greek origin and now also to join word elements of Latin or other origin
speedometerelastomer
-o
10 of 11noun suffix
: one that is, has the qualities of, or is associated with
bucko
-o
11 of 11interjection suffix
—in interjections formed from other parts of speech
cheeriorighto
Synonyms
Noun (1)
- aught
- cipher
- goose egg
- naught
- nought
- nil
- nothing
- oh
- zero
- zilch
- zip
See all Synonyms & Antonyms 
Example Sentences
Noun (1) a word that starts with an o a word that starts with o
Word History
Etymology
Combining form
Greek ōi-, ōio-, from ōion — more at egg entry 1
Affix
Greek, thematic vowel of many nouns and adjectives in combination
Noun suffix
perhaps from oh entry 1
Interjection suffix
probably from oh entry 1
First Known Use
Noun (1)
before the 12th century, in the meaning defined at sense 1a
Noun (2)
1929, in the meaning defined above
Phrases Containing o
Kids Definition
o
1 of 2 nounˈō
often capitalized
1
: the 15th letter of the English alphabet
2
: zero entry 1 sense 1
O
2 of 2variant of oh entry 1
Medical Definition
o-
1 of 4 abbreviation orth-; ortho-
O
2 of 4 noun ˈō
: the one of the four ABO blood groups characterized by the absence of antigens designated by the letters A and B and by the presence of antibodies against these antigens
O
3 of 4 abbreviation1
opening
2
[Latin octarius] pint —used in writing prescriptions
O
4 of 4 symbol oxygen
o
noun
as in oh
the numerical symbol 0 or the absence of number or quantity represented by it our zip code is six-o-three-seven-five Synonyms & Similar Words
Relevance
- oh
- zero
- nothing
- nil
- aught
- naught
- nought
- zip
- goose egg
- zilch
- cipher
- void
- blank
- turbofan
- turbofans
- turbogenerator
- turbogenerators
- turbojet
- turbojet engine
- turbojets
- turbomachineries
- turbomachinery
- turboprop
- turboprop engine
- turboprop-jet engine
- turboprops
- turbopump
- turboramjet engine
- turbos
- turboshaft
- turboshafts
- turbosupercharged
- turbosupercharger
- turbosuperchargers
- turbot
- turbotrain
- turbotrains
- turbots