الضُّحَى

A word in the Arabic language will either be 1) a verb or 2) a noun or 3) a particle – الضُّحَى is a noun

A noun may either be 1) Definite or indefinite 2) Masculine or feminine 3) Singular, dual or plural 4) Nominative, accusative or genitive

الضُّحَى is the natural state of this definite noun and it remains الضُّحَى even though it is in the genitive case due to: 1) a preposition that precedes it or 2) a possessed noun that precedes it or 3) it’s a noun of dependent declension a) نَعْتٌ / صِفَطٌ adjectives b) التَّوْكِيْدُ emphatic c) المَعْطُوْفٌ conjunction d) البَدَلُ synonym

The third radical in الضُّحَى is a weak letter (و or ي) weak letters do not show their endings, their endings have to be estimated (deduced by reason)

Brightness of the day

To be smitten by sunbeams, suffer from the heat of the sun, become uncovered, be revealed, appear conspicuously

مَعْرِفَةٌمُفْرَدٌمُذَكَّرٌمَجْرُوْرٌض ح وبَاب فَتَحَضَحَى يَضْحَىفُعَلٌاسْمٌالْاِسْمُ الجِنْسُ
DefiniteSingularMasculineGenitiveRootDaylightفPatternNounGeneric / common noun
Surah/Below is the only verse in the holy Quran containing the genitive nounالضُّحَى
Verse
93-1By the brightness of the day (daylight)وَالضُّحَى