sinus

n. (Anatomy) any of several hollow cavities or passages in the body; one of the hollow cavities in the skull that connects to the nasal passages

Sinus may refer to: In anatomy, where a sinus is a sac or cavity in any organ or tissue:Paranasal sinus, an air cavity in the cranial bones, especially those near the nose Sinus (anatomy), description of the general termAnal sinuses, the furrows which separate the columns in the rectum Dural venous sinuses, venous channels found between layers of dura mater in the brain
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Sinus /si·nus/ pl. si´nus, sinuses [L.] 1. a recess, cavity, or channel, as one in bone or a dilated channel for venous blood. 2. [more]Sinus - Community and Resources

Noun
1. an abnormal passage leading from a suppurating cavity to the body surface
(synonym) fistula
(hypernym) passage, passageway
2. any of various air-filled cavities especially in the bones of the skull
(hypernym) cavity, bodily cavity, cavum
(hyponym) ethmoid sinus, ethmoidal sinus, sinus ethmoidales
3. a wide channel containing blood; does not have the coating of an ordinary blood vessel
(synonym) venous sinus
(hypernym) duct, epithelial duct, canal, channel
(hyponym) cavernous sinus, sinus cavernosus

n. sine, ratio of the length of the side opposite an acute angle to the length of the hypotenuse (Trigonometry), sinus, any of several hollow cavities or passages in the body