From the Arabic root ض-و-أ (ḍ-w-ʾ), carrying the core sense of shining and illuminating. Cognate with the Hebrew אוֹר (*ʾôr*, "light") through the broader Semitic root for brightness. The word appears extensively in classical Arabic poetry and the Quran (e.g., Surah Yunus 10:5, where the sun is described as *ḍiyāʾ*, a closely related form).

Light holds deep symbolic weight in Arabic and Islamic culture — the divine epithet *an-Nūr* (النُّور, "The Light") is one of the 99 Names of God. While *ḍawʾ* and *nūr* (نُور) are often used interchangeably in everyday speech, classical scholars distinguish them: *ḍawʾ* refers to light from an original source (like the sun), whereas *nūr* refers to reflected or derived light (like moonlight). This distinction appears in Quranic usage and is a rich topic in Arabic rhetoric (*balāgha*).