sinus

noun

si·​nus ˈsī-nəs How to pronounce sinus (audio)
: cavity, hollow: such as
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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Suffering from a broken rib and sinus infection, Remco Evenepoel hands his bidon to a child on the roadside and dismounts his bike. — Jacob Whitehead, New York Times, 2 July 2026 Local residents there have since reported emphysema, pneumonia, bronchitis and sinus infections following the incident, and believe smoke from the fire is the cause, according to a report by Northwest Public Broadcasting. — Josh Boswell, CBS News, 26 June 2026 More than two years later, residents of the surrounding community have reported ongoing problems with their lungs, sinuses and respiratory systems and some have passed away, while livestock and pets have also become ill and died, Sykes said. — Alex Wigglesworth, Los Angeles Times, 23 June 2026 In May, Stewart axed two Las Vegas residency performances while recovering from a sinus infection and undergoing vocal rest. — Ashley Hume, FOXNews.com, 14 June 2026 See All Example Sentences for sinus

Word History

Etymology

Middle English, from Medieval Latin, from Latin, curve, fold, hollow

First Known Use

15th century, in the meaning defined above

Time Traveler
The first known use of sinus was in the 15th century

Phrases Containing sinus

Rhymes for sinus

See All Rhymes for sinus

Browse Nearby Words

sinuous
sinus
sinus gland
See all Nearby Words

Cite this Entry

“Sinus.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/sinus. Accessed 12 Jul. 2026.

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Kids Definition

sinus

noun
si·​nus ˈsī-nəs How to pronounce sinus (audio)
: a hollow place : cavity
especially : any of several cavities in the skull that usually connect with the nostrils

Medical Definition

sinus

noun
si·​nus ˈsī-nəs How to pronounce sinus (audio)
: 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

More from Merriam-Webster on sinus

Nglish: Translation of sinus for Spanish Speakers

Britannica.com: Encyclopedia article about sinus

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