plural of hiddenness

(anatomy) The curving portion of the aorta that bends between the ascending aorta and the descending aorta, from which the brachiocephalic artery, left carotid artery, and left subclavian artery ar...

A person affiliated with an institution in a lesser capacity, for example, as a non-resident or as a part-time affiliate. / A day-scholar. / Outward form or part; exterior.

The quality of being perennial.