The eyebrow is the fold of skin that covers the supraorbital margin. The
hairs that spring from it have a lateral inclination; in elderly people
– especially men – they are thicker and longer than in young
people. The superciliary margin is the thick, curved region
of bone placed a little above the medial part of the supraorbital margin.
It is poorly marked (or even absent in women), but is strongly marked in
men, and is seen better when the eyebrow is marked down. The smooth area
between the right and left arches is called the glabella.