Sinus

n.	1.	An opening; a hollow; a bending.
	2.	A bay of the sea; a recess in the shore.
	3.	(Anat. & Zool.) A cavity; a depression.
	4.	(Med.) A narrow, elongated cavity, in which pus is collected; an elongated abscess with only a small orifice.
	5.	(Bot.) A depression between adjoining lobes. Pallial sinus (Zool.) See under Pallial. Sinus venosus a - (Anat.) The main part of the cavity of the right auricle of the heart in the higher vertebrates. b - In the lower vertebrates, a distinct chamber of the heart formed by the union of the large systematic veins and opening into the auricle.

Noun	1.	sinus - an abnormal passage leading from a suppurating cavity to the body surface Synonyms: fistula
	2.	sinus - any of various air-filled cavities especially in the bones of the skull
	3.	sinus - a wide channel containing blood; does not have the coating of an ordinary blood vessel Synonyms: venous sinus

alveolation, alveolus, antrum, arc, armpit, basin, bow, bowl, catacaustic, catenary, caustic, cavity, circle, concave, concavity, conchoid, crater, crook, crypt, cup, curl, curve, depression, diacaustic, dip, ellipse, festoon, fold, follicle, funnel chest, hole, hollow, hollow shell, hook, hyperbola, lacuna, lituus, parabola, pit, pocket, punch bowl, scoop, shell, sink, socket, tracery, trough, vug