sinus

A depression or cavity formed by a bending or curving.

A dilated channel or receptacle containing chiefly venous blood.

Any of various air-filled cavities in the bones of the skull, especially one communicating with the nostrils.

A fistula leading from a pus-filled cavity.

A recess or indentation between two lobes or segments, as of a leaf.

A bend or fold; a curving part of anything; a sinuosity; specifically, a bay of the sea; a gulf.

In anatomy and zoology, a cavity or hollow of bone or other tissue, in the widest sense; a bay, recess, pocket, dilatation, or excavation, generally deeper and less open than a fossa: used with either English or Latin context.

In pathology, a narrow passage leading to an abscess or other diseased locality; a fistula.

In botany, the recess or rounded curve between two projecting lobes: as, the sinuses of a repand or sinuate leaf. See cuts under kidney-shaped, pinnatifid, repand, and sinuate.