sinus

noun si·nus \ ˈsī-nəs \
Updated on: 15 Nov 2017

Definition of sinus

:cavity, hollow: such as
a :a narrow elongated tract extending from a focus of suppuration and serving for the discharge of pus
b (1) :a cavity in the substance of a bone of the skull that usually communicates with the nostrils and contains air
(2) :a channel for venous blood
(3) :a dilatation in a bodily canal or vessel
c :a cleft or indentation between adjoining lobes (as of a leaf or corolla)

Recent Examples of sinus from the Web

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'sinus.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Origin and Etymology of sinus

Middle English, from Medieval Latin, from Latin, curve, fold, hollow


SINUS Defined for English Language Learners

sinus

noun

Definition of sinus for English Language Learners

  • : any of several spaces in the skull that connect with the nostrils


SINUS Defined for Kids

sinus

noun si·nus \ ˈsī-nəs \

Definition of sinus for Students

:any of several spaces in the skull mostly connected with the nostrils

Medical Dictionary

sinus

noun si·nus \ ˈsī-nəs \

medical Definition of sinus

:a cavity or hollow in the body: as
a :a narrow elongated tract extending from a focus of suppuration and serving for the discharge of pus
  • a tuberculous sinus
b (1) :a cavity in the substance of a bone of the skull that usually communicates with the nostrils and contains air
(2) :a channel for venous blood
(3) :a dilatation in a bodily canal or vessel


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