a
: a narrow elongated tract extending from a focus of suppuration and serving for the discharge of pus
b(1)
: a cavity in the substance of a bone of the skull that usually communicates with the nostrils and contains air
(2)
: a channel for venous blood
(3)
: a dilatation in a bodily canal or vessel
c
: a cleft or indentation between adjoining lobes (as of a leaf or corolla)
Examples of sinus in a Sentence
Recent Examples on the Web
On the moderate end, flu patients may go on to develop ear or sinus infections.
—
Thomas G. Moukawsher, Newsweek, 11 Feb. 2025
Specific health effects People exposed to air pollution can have a number of different symptoms, including burning eyes, sore throat, cough, sinus problems, fatigue, headaches, chest pain, shortness of breath and brain fog, according to Perlmutter.
—Melissa Rudy, Fox News, 13 Jan. 2025
Patients with cancers of the salivary glands, nasal cavity/ear/sinuses, and overlapping head and neck cancers were excluded.
—New Atlas, 30 Dec. 2024
Stage 3: This most advanced stage of HS involves extensive interconnected sinus tracts and widespread scarring or inflammation of the skin.
—Lindsay Curtis, Health, 24 Dec. 2024
See All Example Sentences for sinus
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Thomas G. Moukawsher, Newsweek, 11 Feb. 2025
Specific health effects People exposed to air pollution can have a number of different symptoms, including burning eyes, sore throat, cough, sinus problems, fatigue, headaches, chest pain, shortness of breath and brain fog, according to Perlmutter.
—Melissa Rudy, Fox News, 13 Jan. 2025
Patients with cancers of the salivary glands, nasal cavity/ear/sinuses, and overlapping head and neck cancers were excluded.
—New Atlas, 30 Dec. 2024
Stage 3: This most advanced stage of HS involves extensive interconnected sinus tracts and widespread scarring or inflammation of the skin.
—Lindsay Curtis, Health, 24 Dec. 2024
See All Example Sentences for sinus
Cite this Entry
“Sinus.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/sinus. Accessed 3 Mar. 2025.
Copy CitationKids Definition
Medical Definition
sinus
noun
si·nus
ˈsī-nəs 
: a cavity or hollow in the body: as
a
: a narrow elongated tract extending from a focus of suppuration and serving for the discharge of pus
a tuberculous sinus
b(1)
: a cavity in the substance of a bone of the skull that usually communicates with the nostrils and contains air
(2)
: a channel for venous blood
(3)
: a dilatation in a bodily canal or vessel
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