sinus

American  

[sahy-nuhs] / ˈsaɪ nəs /

noun

plural

sinuses

1. a curve; bend.

2. a curving part or recess.

3. Anatomy.

   1. any of various cavities, recesses, or passages, as a hollow in a bone, or a reservoir or channel for venous blood.

   2. one of the hollow cavities in the skull connecting with the nasal cavities.

   3. an expanded area in a canal or tube.

4. Pathology. a narrow passage leading to an abscess or the like.

5. Botany. a small, rounded depression between two projecting lobes, as of a leaf.

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sinus British  

/ ˈsaɪnəs /

noun

1. anatomy

   1. any bodily cavity or hollow space

   2. a large channel for venous blood, esp between the brain and the skull

   3. any of the air cavities in the cranial bones

2. pathol a passage leading to a cavity containing pus

3. botany a small rounded notch between two lobes of a leaf, petal, etc

4. an irregularly shaped cavity

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sinus Scientific  

/ sī′nəs /

1. A cavity or hollow space in a bone of the skull, especially one that connects with the nose.

2. A channel for the passage of a body fluid, such as blood.

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Other Word Forms

• sinuslike adjective

Etymology

Origin of sinus

1590–1600; < Latin sinus (stem sinu- ) bent or curved surface, curve, fold

Example Sentences

The seeds of Scott’s journey into offshore medical treatments can be traced to about 2002, when he began to experiment with fasting as a way to prevent persistent sinus infections.

From Slate • Mar. 30, 2026

Insmed slumped 15% after the pharmaceutical company ended development of a sinus drug following a failed study.

From Barron's • Dec. 18, 2025

Patel’s opening statement was punctuated by a series of snorts so loud that it seemed he might soon eject a noodle from his sinus cavity.

From Salon • Sep. 17, 2025

He died 10 days later of cerebral venous sinus thrombosis.

From BBC • Aug. 23, 2024

This time I have to have sinus surgery.

From "The Freedom Writers Diary" by The Freedom Writers