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English definition of “sinus”

sinus

noun uk   /ˈsaɪ.nəs/ us  

sinus noun (space in body)

[C] any of the spaces inside the head that are connected to the back of the nose [C] specialized medical a space or passage filled with pus (= a thick yellow liquid) that flows to the surface of the skin

sinus noun (heart)

[U] specialized medical the sinoatrial node (= tissue in the heart responsible for the heart's rhythm): The electrocardiogram will confirm sinus bradycardia.
(Definition of sinus from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
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