sinus

noun

si·​nus ˈsī-nəs 

: 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

Different groups of plants emit pollen to reproduce at various times of the year, causing respiratory and sinus symptoms in some people. —Hayleigh Evans, The Arizona Republic, 21 Sep. 2024

Unwelcome objects — like pollen, pet dander, dust motes, and viral particles — enter our sinuses all the time. —Cody Cottier, Discover Magazine, 8 Aug. 2024

Then comes shedding and pollen season, leaving your sinuses no relief in sight. —Christina Shepherd McGuire, Better Homes & Gardens, 6 Aug. 2024

Plus, staying hydrated allows the cilia in the nose to do their job and push things like bacteria and viruses out of the sinuses, which also can prevent infection. —Amanda Rock, Parents, 30 July 2024

Word History

Etymology

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

First Known Use

15th century, in the meaning defined above

Phrases Containing sinus

• carotid sinus
• coronary sinus
• sinus node
• sinus rhythm
• sinus venosus
• urogenital sinus

Kids Definition

sinus

noun

si·​nus ˈsī-nəs 

: 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 

: 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