A cavity within a bone or other tissue, especially one in the bones of the face or skull connecting with the nasal cavities. noun
She was suffering from a sinus infection that caused severe headaches.
The doctor explained that the sinuses help to humidify the air we breathe.
A channel for the passage of blood or lymph, without the distinct walls of an ordinary vessel. noun
The venous sinus collects blood from the brain and directs it back to the heart.
In some animals, the sinus system is more complex and serves additional functions.
A curve or hollow in a surface, often used in anatomy to describe a depression or cavity. noun
The surgeon noted a sinus in the tissue that needed to be addressed during the procedure.
The anatomical model showed the various sinuses in the human body.