English Reference

Word

oculus

Phoneticsocu·lus

UK/ˈɒkjʊləs/

Definition

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.

Examples

“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.”

Examples

simple

“Light streams through the oculus at the top of the dome.”

contextual

“The architect designed a large oculus to illuminate the central hall without the need for traditional side windows.”

complex

“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.”

Usage

The plural form is 'oculi'.

Real-World Examples

“A plaza between the sections offers shade as well as an oculus: a round opening that allows visitors to “see the sky and the universe”, Yansong told the media.”
The Guardian · 4 Sept 2026

Etymology

Learned borrowing from Latin oculus (“eye”). Doublet of occhio.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Domain

Architecture

This entry

Level
C2 · Proficiency
Frequency
Occasional
Updated

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English Reference