sclera(n = noun.body) sclerotic coat - the whitish fibrous membrane (albuginea) that with the cornea forms the outer covering and protection of the eyeball;
is a kind of albuginea
is a part of eye, oculus, optic

sclera, n. the white of the eye; a white membrane coating the eyeball.

Derivative:
scleral adj. scleritis n. sclerotomy n. (pl. -ies).

Etymology:
mod.L f. fem. of Gk skleros hard