English

Definition of sinus noun from the Oxford Advanced Learner's Dictionary

 

sinus

 noun
noun
BrE BrE//ˈsaɪnəs//
 
; NAmE NAmE//ˈsaɪnəs//
 
 
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any of the hollow spaces in the bones of the head that are connected to the inside of the nose blocked sinuses Word Origin late Middle English (in the medical sense): from Latin, literally ‘a recess, bend’.
See the Oxford Advanced American Dictionary entry: sinus