oculus
n. countable C2 Proficiency UK //ˈɒkjʊləs// ocu·lus
n. a round opening or window in the center of a dome or wall. It lets light and air into a building, often at the very top of a ceiling.
n. a circular opening at the apex of a dome or in a wall. Derived from the Latin word for 'eye', it serves to admit light and reduce the structural weight of the masonry.
Light streams through the oculus at the top of the dome.
The architect designed a large oculus to illuminate the central hall without the need for traditional side windows.
Rainwater falling through the unglazed oculus of the Pantheon is efficiently managed by a sophisticated drainage system built into the slightly slanted marble floor below.
Learned borrowing from Latin oculus (“eye”). Doublet of occhio.
Usage
The plural form is 'oculi'.