sinus

American  

[sahy-nuhs] / ˈsaɪ nəs /

noun

sinuses plural

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 TV broadcast mentioned that Busch had been dealing with a sinus cold all week.

From Los Angeles Times • May 21, 2026

One of her children has developed a sinus condition and another has chronic headaches.

From The Wall Street Journal • May 18, 2026

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

It is also included in a wide range of over-the-counter products for colds, flu, sinus symptoms, and menstrual discomfort.

From Science Daily • Jan. 18, 2026

After a bit of silence, he said, “Hassan is sick. He has a sinus infection.”

From "An Abundance of Katherines" by John Green