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

Explanation

A sinus infection is when the sinuses near your nose get clogged and your face aches. Good times. That’s the kind of sinus people talk about, but a sinus is any kind of space, cavity, or passage in a person's body. When you hear the word sinus, you probably think of the sinuses that can become infected if you have a bad enough cold. You might get a sinus headache when your nose is stuffed up, for example. There are many other sinuses in your body, believe it or not, from the cavernous sinus in your skull to the renal sinuses in your kidneys. The word sinus means "bend, fold, or curve" in Latin.

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

Before undergoing the treatment, performed under local anaesthetic, she said her surgeon told her she would have a sinus lift and a bone graft, along with removing her veneers and having implants put in.

From BBC • Sep. 17, 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

She got sinus headaches that turned to migraines.

From "A Deadly Wandering: A Mystery, a Landmark Investigation, and the Astonishing Science of Attention in the Digital Age" by Matt Richtel