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
1
ocean
2
ohm
3
old
4
order
5
over
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.
: 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
1
offense
2
Ohio
3
[New Latin octarius]
pint
oxygen
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
speedometer
elastomer
: 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
cheerio
righto
Synonyms
Dictionary Entries Near o
Cite this Entry
“O.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/o. Accessed 1 Dec. 2024.
Copy CitationMedical Definition
o-
1 of 4 abbreviation
orth-; ortho-
O
2 of 4 noun
: 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
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