sinus

Meanings

1. 1
   noun

   one of the air-filled cavities in the bones around the nose and eyes that connect with the nasal passages

   Pressure built up in her frontal sinus during the infection.

2. 2
   noun

   a widened channel or cavity that carries venous blood or another bodily fluid

   The scan showed a clot in a venous sinus of the brain.

3. 3
   noun

   an abnormal narrow tract leading from an infected cavity or abscess to the skin or another surface

   The persistent sinus continued to drain fluid from the old wound.

A learned borrowing from Latin sinus ("curve, fold, hollow, bay"). Anatomy applied the image of a hollow or curved recess to cavities and channels within the body. The mathematical word sine is a historical doublet.

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