sinus
//ˈsaɪnəs//
Noun
sinusSingular
sinusesPlural
1
A hollow cavity in the bones of the skull, especially one connecting with the nasal passages.
My sinuses are blocked because of my cold.
2
An abnormal cavity or passage in the body caused by the destruction of tissue, typically resulting from infection or injury.
The doctor discovered a sinus that had formed due to the chronic infection.
3
A dilated channel or vessel, especially one containing blood.
The venous sinus carries blood from the brain back to the heart.