Main Entry:

pto·sis

Pronunciation:

\ˈtō-səs\

Function:

noun

Inflected Form(s):

plural pto·ses \-ˌsēz\

Etymology:

New Latin, from Greek ptōsis act of falling, from piptein

Date:

1743

: a sagging or prolapse of an organ or part ; especially : a drooping of the upper eyelid