oculus

The word "oculus" is a direct borrowing from Latin, where oculus meant "eye". This Latin term itself descends from the Proto-Indo-European root okʷ-, meaning "to see", which is also the ancestor of words like "ocular" and "optic". In architectural terminology, "oculus" was adopted to describe a round, eye-like window or opening, most famously in the dome of the Pantheon in Rome. Thus, the word's journey retains its literal core meaning while being specialized in English to denote a specific architectural feature that visually resembles an eye.

Structure: ocul (eye) + us (noun suffix) - ocul: From Latin oculus, meaning "eye". Its functional role is the core root conveying the core semantic concept of sight or an eye-like structure. - us: A Latin masculine noun ending, indicating the word's grammatical form and origin. In English, it is treated as an integral part of the borrowed noun.