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

Doctors planned to do another transplant after a third round of chemotherapy, but Nicholas continued to experience illnesses and sinus infections. —Sabrina Weiss, People.com, 13 Dec. 2024

Respiratory symptoms may also be a sign of allergies, whooping cough, Valley fever, pneumonia or a sinus infection. —Lauren De Young, The Arizona Republic, 3 Dec. 2024

Although modern cetacean sinus systems help to mitigate ocean pressure around their skulls, a metriorhynchid’s larger snout sinuses would have done the opposite. —Andrew Paul, Popular Science, 30 Oct. 2024

These infections can also spread to the jaw bones or sinuses. —Mark Gurarie, Health, 9 Oct. 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